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!

obviously msg[datalen] is an off-by-one

this fixes a bug introduced with the prefork mechanics: every server process shared the same socket, and this would cause a race condition when multiple server processes asked for a script cgi being executed. This gives each server process its own socket to talk to the executor, so the race cannot happen.