1. Convert the tstate saved in the pcb to a pstate and test for PSTATE_PEF to determine if a process is using floating point. in order to avoid sign extending a 13 bit immediate.
2. We don't need to context switch cwp anymore, it is better to just fiddle the save tstate on return from traps. See exception.s 1.10 and 1.12.
3. Completely remove pcb_cwp.
4. Implement vmapbuf, vunmapbuf and vm_fault_quick. Completely remove TODOs from vm_machdep.c (yay!).

Submitted by: tmm (1, 3, 4)
Obtained from: existing archs (4)