* mips-xdep.c (REGISTER_PTRACE_ADDR, fetch_inferior_registers,

* mips-xdep.c (REGISTER_PTRACE_ADDR, fetch_inferior_registers,
store_inferior_registers):  Replace unexplained numbers
with manifest constants from a DECstation header file.
* xm-mips.h (KERNEL_U_ADDR):  Get from <machine/param.h>.
(REGISTER_U_ADDR):  Fix up for Ultrix 4.2.

* tm-tahoe.h, xm-tahoe.h (KERNEL_U_ADDR):  Move macro to xm-tahoe.h.

* stack.c (_initialize_stack):  "dow" should be a valid abbreviation
for "down".  Suggested by Richard Stallman.