Microsoft EH tests


I’ve started opening up some the MS EH compiler tests here: It’s real limited at this point. Not in the LLVM harness, not fully worked out on other platforms, etc., but I thought it’d be good to get some of the tests open since the WinEH prepare/lower phase is underway. The tests included so far are the “important ones” (in my opinion). The ones you really want to run when you make a change that touches EH.

Feel free to PR anything that helps get these tests moved in the direction of the LLVM test-suite.