Revert a series of commits to MCJIT to get the build working in CMake

(and hopefully on Windows). The bots have been down most of the day
because of this, and it's not clear to me what all will be required to
fix it.

The commits started with r153205, then r153207, r153208, and r153221.
The first commit seems to be the real culprit, but I couldn't revert
a smaller number of patches.

When resubmitting, r153207 and r153208 should be folded into r153205,
they were simple build fixes.

llvm-svn: 153241