MC: Tidy up.

Clean up some simple code quality issues. Bring internal naming
conventions up to current standard, fix inconsistent formatting, and
tidy up a couple of odd contructs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191117 91177308-0d34-0410-b5e6-96231b3b80d8