Added helper functions to the fast code generator for temporary, ad hoc
fixed register allocation.  Also inlined some helper functions that had only
one call site to simplify the code generator API for now.

Review URL: http://codereview.chromium.org/586002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3818 ce2b1a6d-e550-0410-aec6-3dcde31c8c00