remove more cruft

Reference: /n/patches.lsub.org/patch/rmjunk
Date: Thu Jun 21 11:13:10 CES 2012
Signed-off-by: quanstro@quanstro.net

# rm /sys/src/nix/k10/nixtype
# rm /sys/src/nix/k10/root
# rm /sys/src/nix/k10/acore.c.old
# rm /sys/src/nix/k10/fpu.c.old
# rm /sys/src/nix/words