gst/gstpad.c: Don't allow activation of a srcpad in pull_range if it has no getrange...

gst/gstpad.c: Don't allow activation of a srcpad in pull_range if it has no getrange function.

Original commit message from CVS:
* gst/gstpad.c: (gst_pad_activate_pull), (gst_pad_link_prepare):
Don't allow activation of a srcpad in pull_range if it has no
getrange function.
Change some debug statements to be a little clearer

* plugins/elements/gsttypefindelement.c:
(gst_type_find_handle_src_query):
Check that we have a peer before executing queries thereupon.

* tests/examples/metadata/read-metadata.c: (message_loop):
Use gst_bus_pop instead of gst_bus_poll when we just want it to
immediately return us any available message with 0 timeout.