MS ABI: Simplify mangleTemplateArgs

No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@205154 91177308-0d34-0410-b5e6-96231b3b80d8
MS ABI: Correct typo in mangleStringLiteral

No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@205156 91177308-0d34-0410-b5e6-96231b3b80d8