- takes into account new scoping rules

DELTA=52  (21 added, 7 deleted, 24 changed)
OCL=33967
CL=33982

R=rsc
OCL=33974
CL=33974

interpreter values.  Also, print nil values properly.

R=rsc
APPROVED=rsc
DELTA=173  (173 added, 0 deleted, 0 changed)
OCL=33837
CL=33973

- remove visitor pattern interface (not used)
- added non-exported "branding" methods to enforce
  node hierarchy

R=rsc
DELTA=174  (13 added, 92 deleted, 69 changed)
OCL=33838
CL=33963

R=rsc
APPROVED=rsc
DELTA=114  (114 added, 0 deleted, 0 changed)
OCL=33957
CL=33962

In the process, I made error handling in the statement
compiler much saner.  Instead of separately tracking various
error flags with weird relations, I just track if any error
messages have been produced.

R=rsc
APPROVED=rsc
DELTA=308  (98 added, 135 deleted, 75 changed)
OCL=33870
CL=33961

also drop bool arg from ReadString

R=r
DELTA=45  (13 added, 1 deleted, 31 changed)
OCL=33923
CL=33960

R=r
DELTA=63  (23 added, 31 deleted, 9 changed)
OCL=33932
CL=33959

to write type descriptors for ideal types

R=ken
OCL=33958
CL=33958

implicitly works around 6g bug.

R=rsc
OCL=33953
CL=33953

maketables now has a --test option to verify the data.

R=rsc
DELTA=3087  (1982 added, 1001 deleted, 104 changed)
OCL=33947
CL=33950

R=rsc
APPROVED=r,rsc
DELTA=244  (244 added, 0 deleted, 0 changed)
OCL=33733
CL=33940

R=rsc
OCL=33936
CL=33936

R=r,rsc
APPROVED=rsc
DELTA=194  (97 added, 32 deleted, 65 changed)
OCL=33861
CL=33933

R=rsc
DELTA=792  (398 added, 383 deleted, 11 changed)
OCL=33919
CL=33921

R=rsc
DELTA=18  (18 added, 0 deleted, 0 changed)
OCL=33914
CL=33917

use it to limit data read from http.Request Body

R=r
DELTA=32  (8 added, 6 deleted, 18 changed)
OCL=33899
CL=33916

the last bit of data.

add a new iotest.DataErrReader for tests

R=r
DELTA=93  (41 added, 31 deleted, 21 changed)
OCL=33897
CL=33915

R=r
OCL=33913
CL=33913

R=gri
DELTA=105  (77 added, 23 deleted, 5 changed)
OCL=33890
CL=33910

after this CL, two more to come:
	1) add an exhaustive test, probably as a variant of maketables
	2) add ToUpper, ToLower, ToTitle and associated tests

R=rsc
DELTA=1578  (1007 added, 559 deleted, 12 changed)
OCL=33902
CL=33907

R=r
DELTA=1  (1 added, 0 deleted, 0 changed)
OCL=33887
CL=33904

R=rsc
DELTA=1  (1 added, 0 deleted, 0 changed)
OCL=33891
CL=33891

R=rsc
DELTA=113  (10 added, 30 deleted, 73 changed)
OCL=33877
CL=33882

R=r
DELTA=45  (45 added, 0 deleted, 0 changed)
OCL=33873
CL=33881

R=r
DELTA=60  (56 added, 3 deleted, 1 changed)
OCL=33868
CL=33872

R=rsc
DELTA=192  (192 added, 0 deleted, 0 changed)
OCL=33853
CL=33864

statement compiler will be fixed in a later CL.

The input and output of the expression compiler are now
clearly distinguished.  In the process, I made the individual
expression compilers operate on the compiled form of their
children instead of AST nodes.  As a result, there are now
fewer places where I hand-craft intermediate expression nodes.

The diff looks scarier than it is, mostly because exprCompiler
has been split into the input and output types, resulting in
lots of little renames.

R=rsc
APPROVED=rsc
DELTA=774  (204 added, 199 deleted, 371 changed)
OCL=33851
CL=33851

R=rsc
DELTA=444  (179 added, 177 deleted, 88 changed)
OCL=33847
CL=33849

R=r
DELTA=616  (598 added, 11 deleted, 7 changed)
OCL=33846
CL=33848

better FFI demo: compute fibonacci numbers using FFI'ed libgmp.

R=r
DELTA=281  (255 added, 19 deleted, 7 changed)
OCL=33815
CL=33820

Be more conservative: only mess with text/html and text/plain output.

R=rsc
APPROVED=rsc
DELTA=20  (12 added, 5 deleted, 3 changed)
OCL=33806
CL=33812

R=r
DELTA=494  (492 added, 0 deleted, 2 changed)
OCL=33784
CL=33810

move out of export data into its own section

R=r
DELTA=222  (71 added, 99 deleted, 52 changed)
OCL=33801
CL=33808

R=ken
OCL=33792
CL=33803

R=gri
DELTA=20  (17 added, 0 deleted, 3 changed)
OCL=33793
CL=33802

in a .6 file, an export line

	//ffi T localfib remotefib remote.so

means the dynamic linker should initialize
localfib, always a pointer, to the address of
remotefib, either text (T) or data (D) after
loading remote.so.

the C compiler will generate an export section
when given the pragmas

	#pragma package fib
	#pragma ffi T localfib remotefib remote.so

needing #pragma package is a bit of a kludge
and hopefully could go away later.

this is just the 6 tool chain support.
other architectures will happen once 6 settles down.

code using this to do FFI is in a later CL.

R=r
DELTA=161  (141 added, 14 deleted, 6 changed)
OCL=33783
CL=33795

R=rsc
DELTA=1  (0 added, 0 deleted, 1 changed)
OCL=33788
CL=33791

bug192.go:11:5: error: redefinition of ‘fmt’
bug192.go:9:8: note: previous definition of ‘fmt’ was here

R=r
DELTA=2  (0 added, 0 deleted, 2 changed)
OCL=33780
CL=33790

R=rsc
DELTA=9  (5 added, 0 deleted, 4 changed)
OCL=33768
CL=33785