(sim-core.o): Delete duplicate dependence on $(SIM_EXTRA_DEPS).
(sim-cpu.o,sim-endian.o,sim-hw.o): Ditto.
(cgen-run.o,cgen-scache.o,cgen-trace.o,cgen-utils.o): Delete
explicit cgen header dependencies, require SIM_EXTRA_DEPS to include
CGEN_INCLUDE_DEPS.
* cgen-cpu.h: New file.
* cgen-engine.h: New file.
* cgen-scache.h: New file.
* cgen-sim.h: Delete portions moved to new files.
* genmloop.sh: Generate two files eng.hin,mloop.cin explicitly,
rather than sending result to stdout.