(include_subdirs qualified) for OCaml libraries and executables

Aliasing

We now build an alias module for every directory. To build a module x/y/z.ml, we need to open -open X -open Y. Similarly, we can write an "interface module" for every directory:

$ ls -R
bar/
  foo.ml
  bar.ml

In this example, Bar.Foo isn't accessible unless it's re-exported by bar.ml

Ocamldep Hacks

Currently ocamldep can't give us precise deps in situations such as:

$ ls -R
bar/
  baz.ml
foo.ml
$ cat foo.ml
let _ = Bar.Baz.foo

ocamldep gives us Bar, even though we really want to know that it's Lib__Bar__Baz that we need. For now we just depend on everything in bar/. Hopefully codept will help us out here.

TODO

• aliasing scheme
• dune-package support
• interface files for module groups
• merlin support
• ppx
• fix describe

Out of scope (for subsequent PR's):

• documentation
• per module preprocessing, virtual libraries, modules without implementation, private modules
• unwrapped libraries
• support in bootstrap