This gives accurate line numbers to inlined functions from another
package. Previously AST nodes from another package would get the line
number of the import statement for that package.

The following benchmark results show how the size of package export data
is impacted by this change. These benchmarks were created by compiling
the go1 benchmark and running `go tool pack x` to extract the export
data from the resulting .a files.

name                                          old bytes   new bytes    delta
bufio                                         3.59k ± 0%   4.17k ± 0%  +16.25%
bytes                                         5.51k ± 0%   6.40k ± 0%  +16.21%
compress/bzip2                                2.69k ± 0%   3.21k ± 0%  +19.74%
compress/flate                                5.14k ± 0%   5.57k ± 0%   +8.43%
compress/gzip                                 8.91k ± 0%  10.46k ± 0%  +17.32%
container/list                                1.76k ± 0%   2.13k ± 0%  +21.51%
context                                       4.51k ± 0%   5.47k ± 0%  +21.43%
crypto                                        1.11k ± 0%   1.13k ± 0%   +1.90%
crypto/aes                                      475 ± 0%     475 ± 0%   +0.00%
crypto/cipher                                 1.18k ± 0%   1.18k ± 0%   +0.00%
crypto/des                                      502 ± 0%     502 ± 0%   +0.00%
crypto/dsa                                    5.96k ± 0%   6.54k ± 0%   +9.82%
crypto/ecdsa                                  6.93k ± 0%   7.69k ± 0%  +10.91%
crypto/elliptic                               6.53k ± 0%   7.17k ± 0%   +9.72%
crypto/hmac                                     464 ± 0%     464 ± 0%   +0.00%
crypto/internal/cipherhw                        313 ± 0%     313 ± 0%   +0.00%
crypto/md5                                      695 ± 0%     711 ± 0%   +2.30%
crypto/rand                                   5.62k ± 0%   6.21k ± 0%  +10.44%
crypto/rc4                                      512 ± 0%     512 ± 0%   +0.00%
crypto/rsa                                    7.31k ± 0%   8.10k ± 0%  +10.86%
crypto/sha1                                     760 ± 0%     777 ± 0%   +2.24%
crypto/sha256                                   523 ± 0%     523 ± 0%   +0.00%
crypto/sha512                                   663 ± 0%     663 ± 0%   +0.00%
crypto/subtle                                   873 ± 0%    1007 ± 0%  +15.35%
crypto/tls                                    29.6k ± 0%   33.8k ± 0%  +14.03%
crypto/x509                                   18.7k ± 0%   21.0k ± 0%  +12.56%
crypto/x509/pkix                              10.6k ± 0%   12.2k ± 0%  +15.22%
encoding                                        473 ± 0%     473 ± 0%   +0.00%
encoding/asn1                                 1.42k ± 0%   1.50k ± 0%   +5.99%
encoding/base64                               1.69k ± 0%   1.80k ± 0%   +6.88%
encoding/binary                               2.76k ± 0%   3.51k ± 0%  +27.09%
encoding/gob                                  13.5k ± 0%   15.2k ± 0%  +12.98%
encoding/hex                                    857 ± 0%     881 ± 0%   +2.80%
encoding/json                                 12.5k ± 0%   14.9k ± 0%  +19.37%
encoding/pem                                    484 ± 0%     484 ± 0%   +0.00%
errors                                          361 ± 0%     370 ± 0%   +2.49%
flag                                          10.5k ± 0%   12.1k ± 0%  +14.92%
fmt                                           1.42k ± 0%   1.42k ± 0%   +0.00%
go/ast                                        15.8k ± 0%   17.5k ± 0%  +10.31%
go/parser                                     8.13k ± 0%   9.86k ± 0%  +21.28%
go/scanner                                    3.94k ± 0%   4.53k ± 0%  +14.73%
go/token                                      3.53k ± 0%   3.75k ± 0%   +6.11%
hash                                            507 ± 0%     507 ± 0%   +0.00%
hash/crc32                                      685 ± 0%     685 ± 0%   +0.00%
internal/nettrace                               474 ± 0%     474 ± 0%   +0.00%
internal/poll                                 7.23k ± 0%   8.38k ± 0%  +15.90%
internal/race                                   511 ± 0%     515 ± 0%   +0.78%
internal/singleflight                           969 ± 0%    1075 ± 0%  +10.94%
internal/syscall/unix                           427 ± 0%     427 ± 0%   +0.00%
io                                            3.52k ± 0%   3.69k ± 0%   +4.82%
io/ioutil                                     8.48k ± 0%   9.90k ± 0%  +16.72%
log                                           5.06k ± 0%   5.98k ± 0%  +18.15%
math                                          4.02k ± 0%   4.35k ± 0%   +8.26%
math/big                                      9.28k ± 0%   9.94k ± 0%   +7.13%
math/bits                                     3.47k ± 0%   4.33k ± 0%  +24.83%
math/rand                                     1.30k ± 0%   1.32k ± 0%   +2.00%
mime                                          2.98k ± 0%   3.70k ± 0%  +24.21%
mime/multipart                                3.68k ± 0%   4.22k ± 0%  +14.65%
mime/quotedprintable                          2.26k ± 0%   2.65k ± 0%  +17.60%
net                                           23.0k ± 0%   25.7k ± 0%  +11.74%
net/http                                      59.1k ± 0%   66.7k ± 0%  +13.00%
net/http/httptest                             35.3k ± 0%   40.9k ± 0%  +15.80%
net/http/httptrace                            15.3k ± 0%   17.6k ± 0%  +15.26%
net/http/internal                             2.77k ± 0%   3.27k ± 0%  +17.89%
net/textproto                                 4.60k ± 0%   5.25k ± 0%  +14.22%
net/url                                       1.73k ± 0%   1.84k ± 0%   +6.59%
os                                            14.3k ± 0%   16.4k ± 0%  +14.86%
path                                            589 ± 0%     606 ± 0%   +2.89%
path/filepath                                 5.07k ± 0%   6.17k ± 0%  +21.79%
reflect                                       6.43k ± 0%   6.81k ± 0%   +5.90%
regexp                                        5.88k ± 0%   6.46k ± 0%   +9.77%
regexp/syntax                                 3.24k ± 0%   3.29k ± 0%   +1.73%
runtime                                       13.1k ± 0%   14.9k ± 0%  +13.73%
runtime/cgo                                     229 ± 0%     229 ± 0%   +0.00%
runtime/debug                                 4.23k ± 0%   5.15k ± 0%  +21.79%
runtime/internal/atomic                         905 ± 0%     905 ± 0%   +0.00%
runtime/internal/sys                          2.04k ± 0%   2.20k ± 0%   +7.64%
runtime/pprof                                 4.73k ± 0%   5.65k ± 0%  +19.41%
runtime/trace                                   354 ± 0%     354 ± 0%   +0.00%
sort                                          1.68k ± 0%   1.85k ± 0%  +10.17%
strconv                                       1.85k ± 0%   1.95k ± 0%   +5.51%
strings                                       3.98k ± 0%   4.53k ± 0%  +13.91%
sync                                          1.52k ± 0%   1.58k ± 0%   +4.28%
sync/atomic                                   1.60k ± 0%   1.74k ± 0%   +8.50%
syscall                                       53.3k ± 0%   54.3k ± 0%   +1.84%
testing                                       8.77k ± 0%  10.09k ± 0%  +14.96%
testing/internal/testdeps                       598 ± 0%     600 ± 0%   +0.33%
text/tabwriter                                3.63k ± 0%   4.41k ± 0%  +21.64%
text/template                                 15.7k ± 0%   18.1k ± 0%  +15.67%
text/template/parse                           9.12k ± 0%  10.35k ± 0%  +13.48%
time                                          6.38k ± 0%   7.14k ± 0%  +11.81%
unicode                                       4.62k ± 0%   4.66k ± 0%   +0.98%
unicode/utf16                                   707 ± 0%     791 ± 0%  +11.88%
unicode/utf8                                  1.06k ± 0%   1.20k ± 0%  +12.63%
vendor/golang_org/x/crypto/chacha20poly1305   1.26k ± 0%   1.43k ± 0%  +13.54%
vendor/golang_org/x/crypto/curve25519           392 ± 0%     392 ± 0%   +0.00%
vendor/golang_org/x/crypto/poly1305             426 ± 0%     426 ± 0%   +0.00%
vendor/golang_org/x/net/http2/hpack           4.75k ± 0%   5.77k ± 0%  +21.42%
vendor/golang_org/x/net/idna                    355 ± 0%     355 ± 0%   +0.00%
vendor/golang_org/x/net/lex/httplex             616 ± 0%     644 ± 0%   +4.55%
vendor/golang_org/x/net/proxy                 7.76k ± 0%   9.58k ± 0%  +23.37%
vendor/golang_org/x/text/transform            1.31k ± 0%   1.32k ± 0%   +0.46%
vendor/golang_org/x/text/unicode/norm         5.89k ± 0%   6.84k ± 0%  +16.06%
vendor/golang_org/x/text/width                1.24k ± 0%   1.27k ± 0%   +2.66%
[Geo mean]                                    2.51k        2.74k        +9.14%

Change-Id: I9ded911bb0ff63c530795fc85253d76b56d8abbc
Reviewed-on: https://go-review.googlesource.com/37239
Run-TryBot: David Lazar <lazard@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>