erlang: add devel branch for 17.0-rc2

OTP 17.0 is a significant release, introducing a number of incompatible changes, including default utf-8 format for source files, but also, finally, compatibility with wxwidgets 3.0.0. This makes all the cool erlang UI debugging tools work OOTB on OSX.

This patch allows a simple:

```
brew update
brew install wxmac
brew install --no-docs --with-sctp --with-dirty-schedulers --time --devel -v erlang
 ```

<3 your work brewmeisterins and brewmeisters!