Fixed "ArgSize may be used uninitialised" error when compiling with gcc.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@192570 91177308-0d34-0410-b5e6-96231b3b80d8
Fix use-after-free in PPCallbacksTest detected by ASan bootstrap bot

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@192572 91177308-0d34-0410-b5e6-96231b3b80d8