freebsd-based names for filenames. This allows us to eliminate
almost all of the uses of ${MACHINE_ARCH} here to do special things, and
instead we use it to include filenames. This makes new architectures easier
to support.
least on i386)... fbsd-* changes started out as s/linux/fbsd/g and then
additional changes to handle different ptrace defines among other things..
(use vfork to eliminate a race for progress group creation)
reg-i386.c is generated by regdat.sh..