gpio exits on module reload and segfaults

While developing code, I use rebar3 auto. After compiling some code changes, the process which opened a gpio line event gets a {‘EXIT’, _, killed}. On receiving the EXIT, I stop the controlling process so the its supervisor can restart it. However, I get a seqfault now.

Reproduce the module-reload scenario described in the issue with rebar3 auto, where a GPIO line event process receives an EXIT and the supervisor restarts it. Trace the GPIO event process and its shutdown path; done means the process can be restarted after reload without a segmentation fault.

Written by the indexing model from the issue text.