gst/gsturi.c: If there's no hostname, we want to return 'c:/foo/bar.txt' and not '/c:/foo/bar.txt' on Windows. Fixes ...

Original commit message from CVS:
* gst/gsturi.c: (gst_uri_get_location):
If there's no hostname, we want to return 'c:/foo/bar.txt'
and not '/c:/foo/bar.txt' on Windows. Fixes #469402.
* tests/check/gst/gsturi.c:
Unit test for the above and a few more things.