8031383: Error recovery in JavacParser could be improved
Summary: Improving error recovery in JavacParser by avoiding artificial nextToken in JavacParser.reportSyntaxError.
Reviewed-by: jjg, jfranck
Contributed-by: dusan.balek@oracle.com, jan.lahoda@oracle.com

8030091: Request to update error messages from javac for negative varargs test cases
Summary: Introducing a new error message for vararg parameter not being the last parameter, improving error message for unexpected character after a parameter.
Reviewed-by: jjg, sogoel