'make quickcheck': don't overwrite debug output.

Achieved by turning optdebug into a first-class compilation mode.

R=bmeurer@chromium.org, machenbach@chromium.org

Review URL: https://codereview.chromium.org/98963002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18236 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix condition in merge-to-branch.sh

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/101973002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18237 ce2b1a6d-e550-0410-aec6-3dcde31c8c00