Got rid of the debug break on return entry code which did not add anything. It just jumped directly to the debug break on return code.

Removed the CodePatcher class on x64 as it was not implemented.

Added instruction cache flush to where the return sequence was patched on x64.

Added some missing ENABLE_DEBUGGER_SUPPORT #ifdef/#endif.
Review URL: http://codereview.chromium.org/193057

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2863 ce2b1a6d-e550-0410-aec6-3dcde31c8c00