I've fixed errors creeped in the last commit in mips_machdep.c.  Sorry
about the mess.  I'll pay full attention next time commit work.

The 'struct frame', which is located inside 'struct pcb', will be
moved to the top of USPACE in near future.  This would remove several
global variable 'curpcb' references.  The change might be done with
UADDR/KERNELSTACK removal.  

Tohru Nishimura
Nara Institute of Science and Technology