[RFA] deleting breakpoints inside of 'commands'

[Andrew Cagney]

> +      head_cmd = cmd = bs->commands;
> +      bs->commands = NULL;
> +      if (bs->breakpoint_at)
> +        bs->breakpoint_at->commands = NULL;

don, i've reservations about this.  could it leave the bp in an 
undefined state - one of the commands could abort.

hoewever, i am very ok with the theory behind it - the comand sequence 
that is executed shouldn't be affected by commands that update the 
breakpoint.  perhaphs a duplication would be better?

andrew