[C++11] Change DebugInfoFinder to use range-based loops

Also changes the iterators to return actual DI type over MDNode.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204130 91177308-0d34-0410-b5e6-96231b3b80d8
[msan] Kill -msan-store-clean-origin flag.

Not only is it slower than the alternative, but also subtly broken.
This commit does not change the default behavior.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204131 91177308-0d34-0410-b5e6-96231b3b80d8