Fix typo in #undef parameter

BUG=None
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/17176003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15217 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Nuke OS::ReleaseStore, use Release_Store instead

The operation is already implemented in atomicops.h No need to duplicate the code.

BUG=None
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/17222004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15218 ce2b1a6d-e550-0410-aec6-3dcde31c8c00