Outlining code bugs

[yotann]

There are various cases in the outlining code that I haven't fully thought through, and some of them are probably handled incorrectly. If we try to perform actual outlining, this will lead to incorrect code being generated.

• various TODOs and FIXMEs in lib/Outlining
• tests should be much more thorough
• if the original function has an address space, section, comdat, or garbage collector, how should we handle them?
• parameter attributes may be handled incorrectly
• function attributes may be handled incorrectly
  • see constructFunction in llvm/lib/Transforms/Utils/CodeExtractor.cpp
• metadata may be handled incorrectly
  • debug
  • TBAA
  • noalias
  • callback
  • llvm.loop
  • prof

[regehr]

most of this is hopefully not too hard, I think most attributes and metadata can be soundly dropped

[yotann]

For now, I just want the outliner to extract valid functions without crashing. We can worry later about performing the outlining correctly.