1. parser.h depends on ast.h, but only gets it included implicitly
   everywhere parser.h is included (except for tests).  Include ast.h in
   parser.h.

2. Regular expression tests test the free functions that have just been
   moved into class Parser.

TBR=fschneider@chromium.org

Review URL: http://codereview.chromium.org/3602007

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5577 ce2b1a6d-e550-0410-aec6-3dcde31c8c00