Remove support for nand atomic builtins. They are inconsistently implemented in
gcc, and the common expectation seems to be that they are unused. If and when
someone cares we can add them back with well documented demantics.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@99522 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed