watchdog: reworked to add support for software reset.

support for reset due to watchdog timeout...  at the same time more
	strict based on watchdog documentation.

	modified:   sim/avr_watchdog.c
		largely rewritten to support software reset.

	modified:   sim/avr_watchdog.h
		data record added to support software reset

	modified:   sim/sim_regbit.h
		two new functions used in additions to get regbit from value
			and set array of registers from a value