The PNaCl target no longer permits __attribute__((regparm)).

Remove the custom lowering code dealing with it, disallow it in PNaclTargetInfo
and adjust tests accordingly.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179059 91177308-0d34-0410-b5e6-96231b3b80d8