can extract import "C" doc comment
and all references to C package.

; cgo gmp.go | sort
#include <gmp.h>
gmp.go:197:4: mpz_t as type
gmp.go:205:2: mpz_init as call
gmp.go:206:2: mpz_set as call
gmp.go:221:2: mpz_init as call
gmp.go:227:7: size_t as call
gmp.go:228:2: mpz_export as call
gmp.go:235:13: mpz_sizeinbase as call
gmp.go:241:2: mpz_set as call
gmp.go:252:3: mpz_import as call
gmp.go:261:2: mpz_set_si as call
gmp.go:273:5: mpz_set_str as call
gmp.go:282:9: mpz_get_str as call
gmp.go:287:3: mpz_clear as call
gmp.go:302:2: mpz_add as call
gmp.go:311:2: mpz_sub as call
gmp.go:320:2: mpz_mul as call
gmp.go:329:2: mpz_tdiv_q as call
gmp.go:339:2: mpz_tdiv_r as call
gmp.go:348:2: mpz_mul_2exp as call
gmp.go:356:2: mpz_div_2exp as call
gmp.go:367:3: mpz_pow as call
gmp.go:369:3: mpz_powm as call
gmp.go:378:2: mpz_neg as call
gmp.go:386:2: mpz_abs as call
gmp.go:404:9: mpz_cmp as call
gmp.go:413:2: mpz_tdiv_qr as call
gmp.go:426:2: mpz_gcdext as call
;

R=r
DELTA=746  (746 added, 0 deleted, 0 changed)
OCL=34710
CL=34714

R=gri
DELTA=29  (10 added, 12 deleted, 7 changed)
OCL=34709
CL=34712

	fmt.Printf("%s: %s\n", expr.Pos(), message);

R=gri
DELTA=15  (1 added, 3 deleted, 11 changed)
OCL=34706
CL=34708

R=rsc
DELTA=152  (6 added, 0 deleted, 146 changed)
OCL=34695
CL=34701

R=rsc
DELTA=1  (0 added, 0 deleted, 1 changed)
OCL=34696
CL=34700

DELTA=9  (2 added, 4 deleted, 3 changed)
OCL=34690
CL=34692

- added TODO for syntax for built-ins (require type as first argument)
- removed duplicate definition of Index

DELTA=13  (11 added, 1 deleted, 1 changed)
OCL=34668
CL=34688

R=gri
DELTA=14  (14 added, 0 deleted, 0 changed)
OCL=34636
CL=34687

R=r
DELTA=940  (929 added, 1 deleted, 10 changed)
OCL=34679
CL=34686

R=r
DELTA=949  (949 added, 0 deleted, 0 changed)
OCL=34676
CL=34678

	no semicolon allowd after package clause.
	semicolon allowed after import statement.
	no doubled semicolons allowed

R=ken
OCL=34674
CL=34674

R=rsc
DELTA=10  (5 added, 0 deleted, 5 changed)
OCL=34662
CL=34666

R=rsc
APPROVED=rsc
DELTA=17  (0 added, 12 deleted, 5 changed)
OCL=34659
CL=34665

R=rsc
APPROVED=rsc
DELTA=12  (11 added, 1 deleted, 0 changed)
OCL=34658
CL=34664

R=rsc
APPROVED=rsc
DELTA=21  (7 added, 5 deleted, 9 changed)
OCL=34607
CL=34663

DELTA=238  (118 added, 116 deleted, 4 changed)
OCL=34653
CL=34660

R=ken
OCL=34657
CL=34657

R=rsc
DELTA=3  (0 added, 0 deleted, 3 changed)
OCL=34654
CL=34656

 * update mksyscall.sh and rebuild syscall/z*.go
 * fix a few linux-only files

R=r
DELTA=455  (12 added, 1 deleted, 442 changed)
OCL=34637
CL=34655

TBR=rsc
DELTA=56  (56 added, 0 deleted, 0 changed)
OCL=34652
CL=34652

- printing of expressions: put spaces only where "needed"
- printing of import statements: no double indentation if there are no renames
- print labels on separate lines
- added extra test files

go/ast:
- unified basic literal nodes and as a result deleted duplicated code
- added initial code to track scopes (not fully used yet)

replaces CL 34553

R=rsc
DELTA=881  (579 added, 223 deleted, 79 changed)
OCL=34623
CL=34651

R=r
DELTA=127  (38 added, 3 deleted, 86 changed)
OCL=34640
CL=34650

DELTA=23  (19 added, 1 deleted, 3 changed)
OCL=34646
CL=34649

DELTA=174  (65 added, 10 deleted, 99 changed)
OCL=34625
CL=34639

the last round omitted := range and only
checked 1 out of N vars in a multi-var :=

R=r
OCL=34624
CL=34638

also template/template.go, missed last time.

R=r
DELTA=116  (61 added, 10 deleted, 45 changed)
OCL=34620
CL=34622

fix some bugs involving _.

R=ken
OCL=34621
CL=34621

SimpleStmt was always used as an option.

fix bug: divide is a right shift

DELTA=8  (0 added, 0 deleted, 8 changed)
OCL=34612
CL=34614

R=r
DELTA=112  (6 added, 57 deleted, 49 changed)
OCL=34610
CL=34610

R=r
DELTA=3  (3 added, 0 deleted, 0 changed)
OCL=34606
CL=34609

R=r
DELTA=2  (1 added, 0 deleted, 1 changed)
OCL=34605
CL=34608

R=ken
OCL=34604
CL=34604

R=gri
DELTA=12  (12 added, 0 deleted, 0 changed)
OCL=34601
CL=34601

R=rsc
DELTA=125  (103 added, 22 deleted, 0 changed)
OCL=34586
CL=34598

the first IDAT chunk.

R=rsc
APPROVED=rsc
DELTA=7  (2 added, 0 deleted, 5 changed)
OCL=34583
CL=34585

R=rsc
DELTA=83  (83 added, 0 deleted, 0 changed)
OCL=34584
CL=34584

DELTA=15  (6 added, 1 deleted, 8 changed)
OCL=34549
CL=34564

R=rsc
APPROVED=r
DELTA=694  (675 added, 3 deleted, 16 changed)
OCL=34427
CL=34554

TBR=rsc
OCL=34550
CL=34552

delay calls to savex as long as possible.

R=ken
OCL=34535
CL=34546