Handle system messages

[essen]

And write a sys_SUITE.

[fishcakez]

Please feel free to use any code, particularly the tests, from the my system message PRs targeting v1.1. Not sure any of it applies anymore but be my guest all the same.

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On 18 Feb 2017 7:59 pm, "Loïc Hoguin" ***@***.***> wrote: And write a sys_SUITE. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#1126>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AB6JTToDVeYKAmRac-9sFxFrb91YqGqrks5rd02NgaJpZM4MFPMm> .

[essen]

Yes! I kept them open specifically for that reason. :-) Thanks!

They probably don't apply anymore since they pre-date the large internal rewrites in 2.0.0-pre.4. But they'll be a good checklist.

Note that this ticket is specifically about handling system messages, the processes already use proc_lib.

[essen]

While I'm here...

#750
#754

[essen]

Man these PRs were huge. I will only respond to system messages first, with no code_change/format_status and such (or rather, not change of state when code_change happens, etc.) and we can see later for bigger and better.

[essen]

This part is done on master.