Stand resume() on its head

[Andrew Cagney <ac131313@redhat.com>]

Hello,

There have now been several discussion threads that lead to the 
conclusion that

	target->resume (ptid_t, int, enum target_signal)

needs changing.  At present the suggestion is to add a parameter to 
indicate schedule locking and similar operations.

I'd like to propose a different approach.  Instead of passing to 
resume() what to do, have resume() iterate over all the threads asking 
each what it should do - suspend, step, run, signal, ...

I think, in the end, GDB will need to do something like this any way 
(how else is GDB going to handle suspended threads?) so might as well 
start earlier rather than later :-)

(thinking out loud)
Andrew