8048805: Request to investigate and update lexer error recovery in javac
8046620: Further investigation needed for few error messages for negative unicode tests in langtools regression ws
8048803: javac should report complete character code in the error messages
Summary: Improving error reporting and recovery in the lexer
Reviewed-by: jjg, mcimadamore
Contributed-by: jan.lahoda@oracle.com, sonali.goel@oracle.com