I.e., don't just convert \u to u in identifiers (like in strings and regexps).

Also make the scanning of RegExp flags not interpret the escapes.

(Fix and reapply of r8942)

BUG=v8:1620
TEST=mjsunit/regress/regress-1620

Review URL: http://codereview.chromium.org/7677012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8969 ce2b1a6d-e550-0410-aec6-3dcde31c8c00