If a breakpoint is not user visible, then there's no point in

If a breakpoint is not user visible, then there's no point in
bothering the frontend about it...  This is the exact same check MI
does.

I also smoke tested Emacs 23 in gud-gdb mode, both annotations=2
and annotations=3.  I didn't notice anything break.

gdb/
2013-01-22  Pedro Alves  <palves@redhat.com>

	* annotate.c (breakpoint_changed): Skip if breakpoint is not
	user-visible.

gdb/testsuite/
2013-01-22  Pedro Alves  <palves@redhat.com>

	* gdb.base/annota1.exp (signal sent): No longer expect
	breakpoints-invalid.
	* gdb.cp/annota2.exp (continue until exit)
	(watch triggered on a.x): Ditto.