Print token string into the syntax error message.

Bison calls yyerror("syntax error") when it cannot match any grammar rule.
We used to append current token string to the error message,
which got broken in r2202.

This patch restores the original behavior.

BUG=442
R=kbr@chromium.org

Review URL: https://codereview.appspot.com/12876043
4 files changed