Implement fast paths for the special cases like PowerOfTwo divisors
and the dividend being smaller than the divisor (non-negative).

BUG=v8:1314

Review URL: http://codereview.chromium.org//6816049

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7704 ce2b1a6d-e550-0410-aec6-3dcde31c8c00