Refactor happyDoActions

[Kariiem]

This PR refactors happyDoActions into several smaller functions, changes how the parsing tables are constructed, using 32-bit integers instead of 16-bit integers.

[sgraf812]

I rebased and added a commit fixing the tests. Feel free to squash the changes in the commits where they belong.

[sgraf812]

Sigh. I just realised I had the following comments stuck in the review queue which we should discuss.

[sgraf812]

I had a closer look at how WORDS_BIGENDIAN is to be used. alex simply pulls it from the GHC-provided header ghcconfig.h. So we need to add the following line to the begin of the template (after the GHC check):

#include "ghcconfig.h"

After that, we still need to add an emulated CI pipeline as suggested by @Bodigrim here: haskell/alex#260 (comment). I can do that as well, but probably not within the next 2 weeks.

[Bodigrim]

I had a closer look at how WORDS_BIGENDIAN is to be used. alex simply pulls it from the GHC-provided header ghcconfig.h.

There are several possible headers; I don't remember why but I think at some point we concluded that MachDeps.h is the best option.

There is also GHC.ByteOrder, but beware that it was broken before GHC 8.10. A compatibility package ghc-byteorder is available.

[sgraf812]

Alright, I included MachDeps.h to import the WORDS_BIGENDIAN define and did a final review. I'm inclined to merge this.