compiler: check arch-dependent implementation

Array lengths and indices are kept 32-bit no matter what arch is chosen;
pointer types and word sizes are in accordance with the arch chosen.
[skip bamboo]

compiler: Implement strictly positive check and recursive parameter shadowing in reorganiser

compiler.dargent: WIP - layout polymorphism

[skip lemma]

compiler.dargent: add syntax for layout polymorphism

[skip lemma]

compiler: fix merge breakage

[skip lemma]

compiler: eliminate trailing spaces

[skip lemma][skip ci]

Setup for implementing separated typechecking and desugaring.

Not sure why `make test-tc` has `fail_wf-take-nonexisting-field.cogent` broken.

Made changes in response to suggestions on pull request.

Haven't changed the type `Size` from `Integer` to `Word32`
because it breaks the quickCheck tests - causes an infinite loop,
I'm guessing because it overflows the `Word32` at some point. Not
sure why, can investigate in the future.

compiler: stable names generation (#322)

[skip lemma]

compiler: Fix isabelle renaming to be consistent (#301)

* compiler: Fix isabelle renaming to be consistent, integrates with shallow proof
* compiler: add Isabelle name module
* compiler: Remove substript in IsabelleName for invalid names

compiler: Fixed build issue from merge

Comment on isabelle function, new generated embedding

Isabelle embedding now avoids the use of keywords

Working renaming

[Untested] Isabelle name resolution

cogent: [wip] add a repl for cogent

lots of annoying problems are present...
[skip ci][skip lemma]

compiler: individuate the types of function names in core (#273)

compiler: add a simple QuasiQuoter for Cogent

[skip ci]

compiler: deps -= {groups}

[skip lemma]

compiler: TPtr -> Sigil layout

[skip lemma]

compiler: fix array indices eval and core pp

[skip ci]

compiler: largely improve coherence btw parser and pp

Typechecker now does overlapping checks for repr declarations.

compiler: up to core tc.

very coarse. [skip lemma][skip ci]

compiler: wip - arrays (parser, ds).

also fix a lot of code to make it work with ghc-8.4

[skip ci][skip lemma]

compiler: some initial array implementation

[skip lemma][skip ci]

compiler: TBang and TUnbox are properly normalised

compiler: some cleanup and better debugging funcs

normaliseT doesn't normalise enough

compiler: alpha version of ffi-generator

* users can specify customised type generation via --cust-ty-gen flag
* add examples pass_ffi-gen-1
* bump to 2.0.8.0

* todo: put pass_ffi-gen-1 into testsuite

Code reorganisation.

* A rejig of the the Cogent compiler's directory structure.
* Support for building Cogent compiler with both `cabal` and `stack`.
(`stack` support is EXPERIMENTAL)
* Use Makefiles for build and install.
* Remove trailing white-spaces.
* Generate `dummy headers` in `tests/include` for testing C code.
* Remove unused `gen_types.sh` script
* Bump version to `2.0.6`

TODO:
* Remove duplicated files in `libgum`