RFA: fix simulator's handling of exceptions

[Andrew Cagney]

This patch could be totally inept, but with luck, you can see what I
have in mind.  Please clue me in.

2001-05-05  Jim Blandy  <jimb@redhat.com>

* interp.c (program_interrupt): Don't try to emulate the
	processor's behavior when it hits a breakpoint, unless we're
	in the OPERATING_ENVIRONMENT.

I'm not sure this is correct.  The mn10300 doesn't have an operating 
environment (user/supervisor modes).  Have a look at either the d10v or 
the tx39.

In general what happens is:

	o	simulator encounters a breakpoint

	o	simulator saves all state relevant
		to the breakpoint in case it has
		to be delivered

	o	breakpoint encountered (SIGBREAK)
		returned to GDB

	o	GDB checks to see if it is a
		breakpoint on its breakpoint list.

	o	if it is.
		Process the breakpoint and then,
		later when the target is resumed,
		pass in 0 as the signal.

	o	if it isn't
		Depending on the current state of
		SIGBREAK (according to (gdb) handle?)
		possibly resume the target with
		SIGBREAK as the signal.  The target
		simulator should then use that saved
		breakpoint state to deliver a breakpoint
		interrupt to the target.

Andrew