gdb/18216: displaced step+deliver signal, a thread needs step-over, crash

gdb/18216: displaced step+deliver signal, a thread needs step-over, crash

The problem is that with hardware step targets and displaced stepping,
"signal FOO" when stopped at a breakpoint steps the breakpoint
instruction at the same time it delivers a signal.  This results in
tp->stepped_breakpoint set, but no step-resume breakpoint set.  When
the next stop event arrives, GDB crashes.  Irrespective of whether we
should do something more/different to step past the breakpoint in this
scenario (e.g., PR 18225), it's just wrong to assume there'll be a
step-resume breakpoint set (and was not the original intention).

gdb/ChangeLog:
2015-04-10  Pedro Alves  <palves@redhat.com>

	PR gdb/18216
	* infrun.c (process_event_stop_test): Don't assume a step-resume
	is set if tp->stepped_breakpoint is true.

gdb/testsuite/ChangeLog:
2015-04-10  Pedro Alves  <palves@redhat.com>

	PR gdb/18216
	* gdb.threads/multiple-step-overs.exp: Remove expected eof.