Debug Info: Emit vtables pointer members as artificial.

I wasn't sure where to put the test case for this, but this seemed like as good
a place as any. I had to reorder the tests here to make them legible while
still matching the order of metadata output in the IR file (for some reason
making it virtual changed the ordering).

Relevant commit to fix up LLVM to actually respect 'artificial' member
variables is coming once I write up a test case for it.

llvm-svn: 170154