Right now, updating any of the Erlang ports requires generating
patches manually from the git repo, hosting them somewhere, and
hosting the prebuilt BEAM files without which the build can fail
in mysterious and unexpected ways.
By removing all hosted files, lang/erlang will behave like a "normal"
port at last. Also, the big Wx configure patches can go away.
Casualties: erlang-wx is no longer able to build demo.erl, but
that's really minor.