* gencode.c (SDBBP,DERET): Added (3900) insns.
(RFE): Turn on for 3900.
* interp.c (DebugBreakPoint,DEPC,Debug,Debug_*): Added.
(dsstate): Made global.
(SUBTARGET_R3900): Added.
(CANCELDELAYSLOT): New.
(SignalException): Ignore SystemCall rather than ignore and
terminate. Add DebugBreakPoint handling.
(decode_coproc): New insns RFE, DERET; and new registers Debug
and DEPC protected by SUBTARGET_R3900.
(sim_engine_run): Use CANCELDELAYSLOT rather than clearing
bits explicitly.
* Makefile.in,configure.in: Add mips subtarget option.
* configure: Update.