Update gstreamer and friends to 1.14 and some fixes
This also disables gtk-doc documentation for gstreamer and gstreamer-plugins-base, because of https://github.com/mesonbuild/meson/issues/3317
This also disables gtk-doc documentation for gstreamer and gstreamer-plugins-base, because of https://github.com/mesonbuild/meson/issues/3317