This adds an additional step to full gc, removing code from functions
that are no longer in the compilation cache. The code is replaced with
a lazy compile version enabling us to recompile the function in case
we do actually need it again.

Review URL: http://codereview.chromium.org/2632003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4814 ce2b1a6d-e550-0410-aec6-3dcde31c8c00