Unify (Pre)Parser::ParseTryStatement.

Notes:
- This makes Parser and PreParser produce the same errors with the added test
cases (this was not the case before).
- ParseBlock already does Expect(Token::LBRACE), so no need to check it twice.

BUG=v8:3126
LOG=N
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/148233011

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19212 ce2b1a6d-e550-0410-aec6-3dcde31c8c00