Fix pc to code cache so it can cope with a pointer to the start of the code

Fix pc to code cache so it can cope with a pointer to the start of the code
object.  Rename it to be the inner pointer to code cache.
Review URL: http://codereview.chromium.org/7969013

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9336 ce2b1a6d-e550-0410-aec6-3dcde31c8c00