Remove libgstplay, playbin is now the official successor.

Remove libgstplay, playbin is now the official successor.

Original commit message from CVS:
* configure.ac:
* examples/Makefile.am:
* examples/gstplay/.cvsignore:
* examples/gstplay/Makefile.am:
* examples/gstplay/player.c:
* gst-libs/gst/Makefile.am:
* gst-libs/gst/play/.cvsignore:
* gst-libs/gst/play/Makefile.am:
* gst-libs/gst/play/play.c:
* gst-libs/gst/play/play.h:
* gst-libs/gst/play/play.vcproj:
* pkgconfig/Makefile.am:
* pkgconfig/gstreamer-play-uninstalled.pc.in:
* pkgconfig/gstreamer-play.pc.in:
Remove libgstplay, playbin is now the official successor.