[cleanup] Move the Dominators.h and Verifier.h headers into the IR
directory. These passes are already defined in the IR library, and it
doesn't make any sense to have the headers in Analysis.

Long term, I think there is going to be a much better way to divide
these matters. The dominators code should be fully separated into the
abstract graph algorithm and have that put in Support where it becomes
obvious that evn Clang's CFGBlock's can use it. Then the verifier can
manually construct dominance information from the Support-driven
interface while the Analysis library can provide a pass which both
caches, reconstructs, and supports a nice update API.

But those are very long term, and so I don't want to leave the really
confusing structure until that day arrives.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199082 91177308-0d34-0410-b5e6-96231b3b80d8
[cleanup] Switch comments to use '\brief' style instead of '@brief'
style, and remove some unnecessary comments (the code is perfectly
self-documenting here). Also clang-format the function declarations as
they wrap cleanly now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199084 91177308-0d34-0410-b5e6-96231b3b80d8
[cleanup] Fix the includes in the examples for r199082.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199087 91177308-0d34-0410-b5e6-96231b3b80d8