Re: log_min_messages per backend type

Hello

I noticed failures under Windows, and realized that the EXEC_BACKEND
case was busted. That's easy to fix -- just assign MyBackendType in
SubPostmasterMain() as well. With that fix I was still getting some
crashes in three test modules, and after some debugging it turned out
that if you have shared_preload_library with a background worker and use
%b in the log_line_prefix, you get a crash trying to expand a name that
hasn't been set up yet. I figured we can use a constant string in that
case. Better ideas for that string welcome.

So here's your v6 again with those fixes as 0003 -- let's see what CI
thinks of this. I haven't looked at your doc changes yet.

BTW with %b in log_line_prefix, the log file looks ... interesting.

--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
"Before you were born your parents weren't as boring as they are now. They
got that way paying your bills, cleaning up your room and listening to you
tell them how idealistic you are." -- Charles J. Sykes' advice to teenagers