Replace a hand-written suffix compare with std::lexicographical_compare.

No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218380 91177308-0d34-0410-b5e6-96231b3b80d8
Silencing an "enumeral and non-enumeral type in conditional expression" warning. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218381 91177308-0d34-0410-b5e6-96231b3b80d8