to the mips tree.
* Add declarations of functions used by vm_machdep.c.
* Add declarations of functions printed by name in stack tracebacks.
* Add declarations of functions used by the model-independnet mips machdep.c
code.
an vector (struct) of function pointers. Add prototype declarations for
each vector entry.
Add declarations for the r2000 (MIPS-I) and r4000 (MIPS-III) locore
versions of the relevant functions.