Even if we know that the input to a count operation is a smi we still need to check if the result overflowed (and becomes a heap number).

Also fix the smi loop analysis to take two border cases correctly into account.

Review URL: http://codereview.chromium.org/1040002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4147 ce2b1a6d-e550-0410-aec6-3dcde31c8c00