Coverity has generated a number of 'Data race condition' and 'Double
lock' false positives. A lot of these seem to be caused by the NULL
guard in tc_mutex_unlock() not being paired with a NULL guard in
tc_mutex_lock(). This PR adds a NULL guard to tc_mutex_lock().
It should be noted, that on Linux at least, passing NULL to
tc_mutex_lock() causes a segfault. We clearly aren't doing this at the
moment, or we'd know about it. A log message is generated if a NULL
call is made, rather than failing silently.
- xrdp_listen.c is refactored so we can create the
listening socket(s) before dropping privileges.
- The code which reads startup params from xrdp.ini
is moved from xrdp_listen.c to xrdp.c, so it
is only called once if we test the listen before
starting the daemon.
sem_init() is not functional on Mac OS. Use the Grand Central Dispatch
implementation.
Make libscp_lock.c use semaphores through the thread_calls wrapper.
matt335672