Minor cleanup of CompareIC state

Allow transitioning from KNOWN_OBJECT to KNONW_OBJECT or OBJECT.
Also, rename HEAP_NUMBER IC states to NUMBER, since they handle Smis, too.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/12254036

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13775 ce2b1a6d-e550-0410-aec6-3dcde31c8c00