Sorting out some Erlang stuff:
- Rename a few Erlang-related ports using the erlang- prefix; it will avoid confusion with elixir- ports.
- Remove DOCS and EXAMPLES where not actually useful.
- Simplify RUN_DEPENDS where possible.
- Move textproc/exmpp to devel/erlang-exmpp.
- Add missing R18 compatibility fix for devel/erlang-oserl.
- Upgrade erlang-cuttlefish to 2.0.3.
The idea is that libraries ("deps") have the "erlang-" prefix, while larger
projects (rabbitmq, yaws, couchdb, etc) keep their usual names.