code review 1619042: gc: more cleanup

gc: more cleanup
 * disallow surrogate pair runes.
 * diagnose impossible type assertions
 * eliminate another static buffer.
 * do not overflow lexbuf.
 * add -u flag to disable package unsafe.

[rsc, 2010-06-09 18:00:50]

Hello ken2 (cc: golang-dev@googlegroups.com),

I'd like you to review this change.

[rsc, 2010-06-09 18:01:09]

*** Submitted as http://code.google.com/p/go/source/detail?r=53ba4328746e ***

gc: more cleanup
 * disallow surrogate pair runes.
 * diagnose impossible type assertions
 * eliminate another static buffer.
 * do not overflow lexbuf.
 * add -u flag to disable package unsafe.

R=ken2
CC=golang-dev
http://codereview.appspot.com/1619042

[ken3, 2010-06-09 19:53:10]

lgtm