Makes NumberInfo into a real class.
Fix bug where NumberInfo was lost in ToRegister.
Allow 17 bits in safe Smis instead of 16.
Review URL: http://codereview.chromium.org/668151

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4046 ce2b1a6d-e550-0410-aec6-3dcde31c8c00