package/freerdp: re-add support for gstreamer

package/freerdp: re-add support for gstreamer

Previously, we expected the user to select gstreamer-0.x on his own,
to enable gstreamer support in FreeRDP. This could have been a bit
confusing to the user, as he may have enabled gst-1.x but FreeRDP did
only support gst-0.x.

Also, gstreamer support needs xlib-libxrandr, which was missing in
FreeRDP's dependencies, so it was never enabled (AFAICS).

(Re-)introduce support for gstreamer-0.x and gstreamer-1.x, since both
are supported.

We're doing it in a choice, and select whichever version the user chooses,
rather than automatically detect it as previosuly done.  We can select the
gstreamer packages, as their dependencies are anyway already covered by the
ones of FreeRDP.

This also now requires xlib-libxrandr, so hide the choice if X.org is
not enabled, still offer the option of not using gstreamer if it is.

[Peter: Hide option if gstreamer{,1} aren't enabled,
	Default to gstreamer{,1} support enabled
	GStreamer 0.10 support needs host-pkgconf and libxml2]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>