Do not call exit_set inside control coprocessor

	* src/vm/cp0.hh, src/vm/cp0.hxx:
	(get_register) New.
	(raise_overflow, raise_addr_load, raise_addr_store): Activate
	fatal_exception_, remove call to exit_set.
	* src/vm/virtual_machine.cc:
	(execute) Use exit_set to report internal exception.