Original commit message from CVS:
* examples/gstfile.py:
Moved the Discoverer class to gst.extend
Now works asynchronous... bl**dy fast :)
* gst/extend/Makefile.am:
* gst/extend/discoverer.py:
Discoverer has landed in extend and is now asynchronous.
It emits a 'discovered' signal when it has finished.
