HQLPARSER-39 Detection of unconsumed tokens must take non-buffered tokens into account

* ensure the internal token buffer of CommonTokenStream is filled from the underlying TokenSource (lexer) before checking if any tokens are left unmatched
* detect EOF by comparing on token type rather than token text (this is just for efficiency, not actually necessary for fixing the main issue)
* add more trailing token test cases to gUnitHQLGrammar.testsuite
HQLPARSER-40 Making sure legacy "in class" syntax is supported
HQLPARSER-41 Disabling tests using exists clause with legacy join syntax