Changes:
* Replace usage of gettimeofday() with clock_gettime() in the main
event loop, patty_ax25_server_run(), as gettimeofday() apparently
goes backwards in time occasionally, as per:
https://bugzilla.redhat.com/show_bug.cgi?id=174390
Thanks Iain MM0ROR!
* Fix patty_timer_expired() to properly return true if the
remaining number of seconds is zero, but the remaining higher
precision time is less than zero
* Implement patty_timer_sub() to subtract two struct timespec
values, as glibc lacks timespecsub()
XANTRONIX Development
3e51b48453