It's not safe to use an immediate heap object in generated unless we take
pains to ensure it's not in new space.  Continue using the caller's context
for inlined functions on all platforms except IA32.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9427 ce2b1a6d-e550-0410-aec6-3dcde31c8c00