Initial implementation of ad hoc must-be-smi tracking in the fast code
generator.  Type information is used to avoid the write barrier for
smi property stores and to avoid the smi check for the inputs/output
of bitwise OR.

Review URL: http://codereview.chromium.org/597021

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3833 ce2b1a6d-e550-0410-aec6-3dcde31c8c00