[PM] [cleanup] Rename some of the Verifier's members, re-arrange them,
and tweak comments prior to more invasive surgery. Also clean up some
other non-doxygen comments, and run clang-format over the parts that are
going to change dramatically in subsequent commits so that those don't
get cluttered with formatting changes.

No functionality changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199489 91177308-0d34-0410-b5e6-96231b3b80d8