Fun fact: these files used to be called log.[ch] until we ran into
conflicts with systems having a log.h file. But now that we always
include "lib/log/log.h", we should be fine.
This patch:
- introduces an fdio module for low-level fd functions that don't
need to log.
- moves the responsibility for opening files outside of torlog.c,
so it won't need to call tor_open_cloexec.
Previously we had code like this for bad things happening from
signal handlers, but it makes sense to use the same logic to handle
cases when something is happening at a level too low for log.c to be
involved.
My raw_assert*() stuff now uses this code.
(And replay them once we know our first real logs.)
This is an implementation for issue 6938. It solves the problem of
early log mesages not getting sent to log files, but not the issue of
early log messages not getting sent to controllers.
