gst/selector/gstinputselector.c: Add pad property to configure behaviour of the unselected pad, it can return OK or N...

Original commit message from CVS:
* gst/selector/gstinputselector.c: (gst_selector_pad_class_init),
(gst_selector_pad_init), (gst_selector_pad_set_property),
(gst_selector_pad_get_property), (gst_selector_pad_event),
(gst_selector_pad_bufferalloc), (gst_selector_pad_chain),
(gst_input_selector_set_active_pad):
Add pad property to configure behaviour of the unselected pad, it can
return OK or NOT_LINKED, based on the use case.