Lets AI and Borgs control auto announcements

The AI and cyborgs can now control if they speak on the radio and the
channel used when stating laws or  (AI only) announcing new player
arrivals.
Merge remote-tracking branch 'remotes/upstream/master' into Autosay_Fix

Conflicts:
	code/modules/mob/living/silicon/silicon.dm
Adds a changelog

Changelogs because those are important for telling players what changed!
[r] -> [radiomod]

Just changes instances of [r] to [radiomod]. No functional changes.
Merge pull request #6181 from GunHog/Autosay_Fix

Lets AI and Borgs control radio behavior for auto announcements.