* infrun.c (wait_for_inferior): Don't set frame for
step_resume_breakpoint for IN_SIGTRAMP cases.
* infrun.c (wait_for_inferior), breakpoint.h (struct bpstat_what),
breakpoint.c (bpstat_what): Move step_resume from its own field of
the struct bpstat_what into the main_action. Make it override
other breakpoints. This is a conservative change in the sense
that before the step resume breakpoint was a breakpoint.c
breakpoint, hitting the step resume breakpoint overrode even
calling bpstat_stop_status.