VCALLMS-related were found/fixed.
[ChangeLog.sky]
* sky-vu.c ({read,write}_vu_special_reg): Add CMSAR[01] as special
registers for a VU. Behavior not as mandated.
({read,write}_vu_{misc,special}_reg): Create sim_io_error upon
access to unknown register. Behavior not as mandated.
* sky-vu.h (anonymous register numbering enum): Add CMSAR[01].
* sky-libvpe.c (indebug): Cache $ENV{'SKY_DEBUG'}.
[ChangeLog]
* Makefile.in (SIM_SKY_OBJS): Added sky-vudis.o.
* interp.c (decode_coproc): Refer to VU CIA as a "special"
register, not as a "misc" register. Aha. Add activity
assertions after VCALLMS* instructions.