Remove some duplicate functions from the Parser class. Identical functions already exist in the clang namespace from Sema/Ownership.h.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@220896 91177308-0d34-0410-b5e6-96231b3b80d8
Remove the last couple uses of the ExprArg(just Expr*) typedef in Parser.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@220897 91177308-0d34-0410-b5e6-96231b3b80d8