More work on C stub generation.
Add interface for ml_stubs module.
Printer for generated ML stubs.
Generate function for retrieving primitive constructor names.
WIP
Look up the directories for subproject dependencies; don't compute them.
Fix intnat pointer issue in test library.
Generate wrapper functions for ml stubs.

Pass projected raw pointers to C.
Omit trivial wrappers during stub generation.
Order names of naitve/byte functions in external declaration.
Narrow the C_stubs interface.
Generate byte code stub, passing arguments using argc/argv.
Stub generation tests.