assorted underscore cleanup

R=r
DELTA=488  (410 added, 3 deleted, 75 changed)
OCL=25070
CL=25070

	- use a lock instead of a thread in once
		avoids deadlock in recursive once calls
	- implement os.Setenv
	- remove "export" from some scripts
	- remove _ from names in time package
	- fix time test for non-MTV machines

R=r
DELTA=265  (87 added, 58 deleted, 120 changed)
OCL=25057
CL=25057

R=rsc
OCL=25054
CL=25054

as thread-safe as possible, given the surrounding system.
add stub RWLock implementation.

R=r
DELTA=852  (834 added, 6 deleted, 12 changed)
OCL=25046
CL=25053

command-line comment.

R=r
DELTA=11  (6 added, 0 deleted, 5 changed)
OCL=25051
CL=25051

	get rid of _ on private names in net.
	fix os_test file name list.
	newline not needed on Errorf.

R=r
DELTA=305  (34 added, 2 deleted, 269 changed)
OCL=25047
CL=25047

R=r
DELTA=8  (0 added, 6 deleted, 2 changed)
OCL=25045
CL=25045

R=ken
OCL=25044
CL=25044

- remove all parsing heuristics
- as a result, accept a wider syntax, but parser is simpler

R=r
OCL=25029
CL=25029

R=rsc
OCL=25026
CL=25026

- updated some file (but not all - left array package in place for now)

R=rsc
DELTA=530  (483 added, 0 deleted, 47 changed)
OCL=25025
CL=25025

only non-trivial changes are in
	convlit1.go
	golden.out

R=gri
OCL=25019
CL=25024

warn about composite literal { } syntax.

R=ken
OCL=25018
CL=25023

TBR=r
OCL=25021
CL=25021

R=rsc
DELTA=27  (27 added, 0 deleted, 0 changed)
OCL=25015
CL=25015

  (now in sync with the spec and with 6g)
- fixed incorrect logging statement in gds

R=r
OCL=24970
CL=24970

- do not permit + for array concatenation anymore
  (not implemented and not a good idea)
- document that unsafe function results are compile time constants
- fixed minor typos

DELTA=41  (7 added, 11 deleted, 23 changed)
OCL=24899
CL=24927

R=ken
OCL=24350
CL=24914

R=r
OCL=24349
CL=24913

i stumbled across it in all.bash.

TBR=r
OCL=24912
CL=24912

- fixed a syntax error

R=r
DELTA=17  (15 added, 0 deleted, 2 changed)
OCL=24876
CL=24889

- contains a (proposed) constant Maxalign
- contains some text re" alignment guarantees

R=ken,r
DELTA=97  (94 added, 1 deleted, 2 changed)
OCL=24791
CL=24871

R=rsc
DELTA=4  (0 added, 0 deleted, 4 changed)
OCL=24788
CL=24805

R=rsc
DELTA=793  (392 added, 392 deleted, 9 changed)
OCL=24777
CL=24804

the lexer is already hiding names,
so this clumsy hack is no longer necessary.

R=ken
OCL=24783
CL=24783

Refactor so Readdir is portable code.

R=rsc
DELTA=192  (50 added, 130 deleted, 12 changed)
OCL=24770
CL=24772

R=ken
DELTA=20  (19 added, 0 deleted, 1 changed)
OCL=24719
CL=24771

state in the FD.

This is Darwin only.  Next CL will make Readdir use Readdirnames to generate its files
and move Readdir into portable code, as well as fix Readdirnames for Linux.

R=rsc
DELTA=116  (79 added, 12 deleted, 25 changed)
OCL=24756
CL=24768

R=r
DELTA=2  (0 added, 1 deleted, 1 changed)
OCL=24755
CL=24760

- directory listings w/ working links
- some links working in source code (most don't do the right thing yet)
- use of logging

R=r
OCL=24728
CL=24728

R=rsc
DELTA=3  (3 added, 0 deleted, 0 changed)
OCL=24727
CL=24727

R=rsc
DELTA=71  (71 added, 0 deleted, 0 changed)
OCL=24687
CL=24694

R=rsc
OCL=24681
CL=24681

R=rsc
DELTA=200  (176 added, 12 deleted, 12 changed)
OCL=24680
CL=24680

R=gri
OCL=24678
CL=24678

the fix appears to be to align the
out struct on an 8 boundary, but that
is a bit involved.

R=ken
OCL=24657
CL=24657

change type (to satisfy OAS) after nodarg:
nodarg uses offset from type too,
and must use correct offset.

R=ken
OCL=24656
CL=24656

Syscall support.
Readdirnames returns array of strings of contents of directory.

R=rsc
DELTA=216  (201 added, 0 deleted, 15 changed)
OCL=24642
CL=24655

R=rsc
DELTA=21  (2 added, 2 deleted, 17 changed)
OCL=24638
CL=24654

R=rsc
DELTA=9  (3 added, 3 deleted, 3 changed)
OCL=24640
CL=24653