it seems that linux calls the signal handlers even when we're waiting on sigwait for that signal. Work around that.

it's needed by getdtablesize, at least on glibc

before we did `pkill gmid', but that would influence also other instances of gmid!

while there, add capsicum for the logger process

use imsg to handle ALL kinds of IPC in gmid. This simplifies and shorten the code, and makes everything more uniform too.

i.e. don't print scary messages with LOG_CRIT priority!