Simplify test for rdar://19256338
(from patch r224549).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@224713 91177308-0d34-0410-b5e6-96231b3b80d8
Add test coverage for cc1's trigraph option handling.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@224714 91177308-0d34-0410-b5e6-96231b3b80d8