Removed stop sequence when MINIX is shut down.
Disabled send mask checks --- to be replaced by proper mechanism.
Fixed bug relating to 'shutdown -x'.
Simplified clock accounting of realtime.
Updated Makefiles for mkdept script.
when lock timing is enabled in minix/config.h.
Added phys_zero() routine to klib386.s that zeroes a range of memory, and
added corresponding system call.