Checking for end-of-comment truncated to byte before comparing to '*'.

BUG=v8:1546
TEST=mjsunit/regress/regress-1546

Review URL: http://codereview.chromium.org/7585004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8842 ce2b1a6d-e550-0410-aec6-3dcde31c8c00