Also fix the inconsistent attribute naming, and make V8_GNUC_PREREQ() test work for GCC compatible compilers.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/22888008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16311 ce2b1a6d-e550-0410-aec6-3dcde31c8c00