Add functionality for finding code objects from a pc that points into

Add functionality for finding code objects from a pc that points into
the code object's instructions.

This allows us to find a code object using just the pc. This approach
uses a cache (PcToCodeCache) to make sure we don't continuously have
to iterate heap pages.

This change eliminates the need for cooking and uncooking of stack frames.

Review URL: http://codereview.chromium.org/3226014

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5369 ce2b1a6d-e550-0410-aec6-3dcde31c8c00