Re-revert "Use unsigned type bitsets to limit undefined behaviour"

...and the various debug CLs.

R=machenbach@chromium.org
BUG=

Review URL: https://codereview.chromium.org/564413004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23955 ce2b1a6d-e550-0410-aec6-3dcde31c8c00