[PM] Clean up a bunch of comments, modernize the doxygen, nuke some
whitespace, and a couple of argument name fixes before I start hacking
on this code. No functionality changed here.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195699 91177308-0d34-0410-b5e6-96231b3b80d8