Replaced flagalrm() timers with another technique to check for timeouts.

Replaced flagalrm() timers with another technique to check for timeouts.
This allowed removing the p_flagarlm timer from the kernel's process table.
Furthermore, I merged p_syncalrm and p_signalrm into p_alarm_timer to save
even more space. Note that processes can no longer have both a signal and
synchronous alarm timer outstanding as of now.