Add missing header guards.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@215202 91177308-0d34-0410-b5e6-96231b3b80d8
[mips] Add -mabicalls/-mno-abicalls to the driver

Based on a patch by Matheus Almeida. I've added testcases and fixed a bug where
the options weren't passed on to GAS.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@215204 91177308-0d34-0410-b5e6-96231b3b80d8