If the ladspa plugin is enabled explicitly or via auto-features, the
liblrdf dependency can not be disabled.
As the RDF parsing currently provides hardly any features, the possibility
to disable it fairly useful.
Fixes: #3168
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5802>
GLib guarantees libintl is always present, using proxy-libintl as
last resort. There is no need to mock gettex API any more.
This fix static build on Windows because G_INTL_STATIC_COMPILATION must
be defined before including libintl.h, and glib does it for us as part
as including glib.h.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2028>