via cause_sig() during an exception.
moved lock check configuration to <minix/sys_config.h> instead of
kernel/config.h, because the 'relocking' field in kinfo depends on it.
other prettification: common locking macro, whether lock timing is on or
not.
New configuration header file to include/ exclude functionality.
Extracted privileged features from struct proc and create new struct priv.
Renamed various system calls for readability.
Reduced kernel size by 512KB by moving private buffer into cstart() function.
Replaced assertions with erroneous return values. Removed assertions relating
to isuserp(rp), since all processes should become user processes; system
processes are now treated similar to other processes.
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.
