* Using memchr for first/only char lookup is faster than hand-coded
   loop. It processes one machine word per iteration so it helps even
   more on x64.

 * Tweaked badness computation in simple search. We pay only for the
   first char memchr scans, not for all of them.

Review URL: http://codereview.chromium.org/1100002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4173 ce2b1a6d-e550-0410-aec6-3dcde31c8c00