This is definitely not ready for merging. I mainly want to discuss the
Haskell interface we're exposing here. I rebased @scpmw's .debug_ghc section
patch and his Dwarf reading stuff here, just so that the Haskell interface has
some actual working implementation to rely on. As Peter said in D396, he is not
happy with the way the section is generated now (is that correct Peter?).
Please note that this patch set does not yet implement the useful part of being
able to reify the stack automatically on exceptions. So this patch set is still
pretty useless on it's own. But I wanted to keep that change separate, because
it makes changes to critical raise primitive in the RTS. This patch set is
mostly "safe additions", no existing code paths are changed I think.