Eliminate enum bpstat_signal_value, simplify random signal checks further.

Eliminate enum bpstat_signal_value, simplify random signal checks further.

After the previous patch, there's actually no breakpoint type that
returns BPSTAT_SIGNAL_HIDE, so we can go back to having
bpstat_explains_signal return a boolean.  The signal hiding actually
disappears.

gdb/
2013-11-14  Pedro Alves  <palves@redhat.com>

	* break-catch-sig.c (signal_catchpoint_explains_signal): Adjust to
	return a boolean.
	* breakpoint.c (bpstat_explains_signal): Adjust to return a
	boolean.
	(explains_signal_watchpoint, base_breakpoint_explains_signal):
	Adjust to return a boolean.
	* breakpoint.h (enum bpstat_signal_value): Delete.
	(struct breakpoint_ops) <explains_signal>: New returns a boolean.
	(bpstat_explains_signal): Likewise.
	* infrun.c (handle_inferior_event) <random signal checks>:
	bpstat_explains_signal now returns a boolean - adjust.  No longer
	consider hiding signals.