Revert windows-specific part of r15937 for debug level 1.

The change in r15937 might have broken a mozilla test under windows. See https://codereview.chromium.org/19384011/

Each case of debug 0,1,2 is now stated explicitly for better clarity in the msvs section. This causes some minor code duplications, which we can squeeze again after toolchain.gypi is in a stable state.

R=dpranke@chromium.org, jkummerow@chromium.org

Review URL: https://codereview.chromium.org/21495002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16018 ce2b1a6d-e550-0410-aec6-3dcde31c8c00