Rewrite the lazy deopt patching code on IA32 to use addresses throughout,
rather than offsets and a base address.

Also, rename a couple of ambiguous Code fields from _start to _offset.

Review URL: http://codereview.chromium.org/6334083

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6611 ce2b1a6d-e550-0410-aec6-3dcde31c8c00