Add helper functions to the lexer to tokenize strings that have different classifications in ES2 and ES3.

TRAC #23218

Signed-off-by: Geoff Lang
Signed-off-by: Nicolas Capens
Author: Jamie Madill

git-svn-id: https://angleproject.googlecode.com/svn/branches/es3proto@2389 736b8ea6-26fd-11df-bfd4-992fa37f6226