gst/gstpad.c: emit have-data before checking for peers.  This allows for probe handlers to connect elements.  This he...

Original commit message from CVS:
* gst/gstpad.c: (gst_pad_push), (gst_pad_push_event):
emit have-data before checking for peers.  This allows
for probe handlers to connect elements.  This helps autopluggers.
* check/gst/gstpad.c: (GST_START_TEST), (_probe_handler),
(gst_pad_suite):
add six checks, linked/unlinked with no/true/false probe