builtin_recv receives imsg from the client process (it's invoked as `recv' from the scripts) and its interaction with the other process is delicate. Instead of the current mess, try to do a more idiomatic imsg_read/get loop, with a flag to read more messages.

this stuff isn't done as a part of the OpenBSD project obviously.

twstat was truncating out the user mode bits. Found the hard way by cage.