Revert "Disable the step over skipping calls feature since buildbots are not happy."

While this fixed the windows bot failures, it also broke all other bots.

Upon closer inspection, it turns out that the windows bots were "broken"
because two tests were unexpectedly passing -- i.e., the original patch
(r360375) actually improved our stepping support on windows.

So instead, I remove the relevant XFAILs.

This reverts commit r360397.

llvm-svn: 360407