Moved error-handling to a separate class - Diagnostics. We were earlier returning errors as tokens which did not work very well when error occured while parsing a preprocessor directive. Now all returned tokens are valid. Errors are reported via an abstract Diagnostics interface. Updated unit-tests with the new scheme.
Review URL: https://codereview.appspot.com/6203089
git-svn-id: https://angleproject.googlecode.com/svn/trunk@1087 736b8ea6-26fd-11df-bfd4-992fa37f6226
