Remove some unnecessary casts

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172700 91177308-0d34-0410-b5e6-96231b3b80d8
ArrayRef-ize some ctor initializer related APIs

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172701 91177308-0d34-0410-b5e6-96231b3b80d8