Add an option to include headers

[UnkindPartition]

On haskell-packages side: add an option to include CPP headers, analogous to GHC's -optP-include.

On Cabal side: pass cabal_macros.h to the compiler.
See:

• Cabal/Distribution/Simple/GHC.hs:1177
• Cabal/Distribution/Simple/Program/GHC.hs:309

For the background, see haskell-suite/haskell-names#51

[UnkindPartition]

(When this option is added, it'll also have to be handled in hs-gen-iface.)