Various fixes from Ben
- cabal files: Add missing headers to
extra-source-files
to ensure thatcabal sdist
works. - cabal files: Put
GhcDebug.cmm
incmm-sources
rather thanc-sources
. This fixes the lexical errors we were seeing earlier. - cabal files: Drop references to non-existent files as they make
cabal v2-install
upset. - Don't present that unpacked closures are GC pointers. They aren't and the GC will get confused if we say they are.