Reapplication of r4685 (reviewed http://codereview.chromium.org/2101002) with minor modifications:

- Fix compilation problems on Win64.
- Improve heap verification pass: search for garbage pointers to new space not only in dirty regions but in all regions.

Review URL: http://codereview.chromium.org/2114015

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4703 ce2b1a6d-e550-0410-aec6-3dcde31c8c00