Revert "Fix NaCl build."
Revert "Revert target arch detection."
Revert "Fix typo."
Revert "Simplify implementation of Mutex."
Revert "Fix for older clang releases that lack __has_extension."
Revert "Reland initial bits of "Implement correct OS and CC detection.""

TBR=danno@chromium.org,svenpanne@chromium.org

Review URL: https://codereview.chromium.org/21095008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15976 ce2b1a6d-e550-0410-aec6-3dcde31c8c00