Multiple versions or not?
=========================

[ old notes. multi-versioning support was removed for the reasons below ]

Pros:
1. Mistakes or limitations in function definitions can be fixed without ugly
  "_v2" or "_ex" functions
2. API level bugs can be fixed.
3. Behavioral changes can be done.

Cons:
- Limitation: Types cannot be changed, due to the "diamon dependency chain" problem.
- Public constants and inlined functions might not be possible to change in
  practice (for the same reasons as for types)
- Complicates implementation.
- Source code examples could fail to work or do the wrong thing.
- Documentation needs to cover both new and old versions.

Alternative solution with module v2 renames
-------------------------------------------

- Enforce strict add-only versioning (no deletions or changes)
- Allow symbol deprecations (= warning) and symbol hiding (= error)
  in incremental versions.
- Cleanups in major versions can be done as new modules
  (e.g. module 1.9 vs module2 2.0)

With the steps above, mistakes/limitations and API level bugs can be fixed.