Fix all the remaining lost-fast-math-flags bugs I've been able to find. The most...

Fix all the remaining lost-fast-math-flags bugs I've been able to find.  The most important of these are cases in the generic logic for combining BinaryOperators.
This logic hadn't been updated to handle FastMathFlags, and it took me a while to detect it because it doesn't show up in a simple search for CreateFAdd.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199629 91177308-0d34-0410-b5e6-96231b3b80d8