configure: check for plugins-base and others (bgo#721587)
configure: check for plugins-base and others (bgo#721587)

This would prevent a build failure when trying to 'make' the glue:

generated.c: In function 'gst__tagssharp_gst__tags_tagdemux_get_element_offset':
generated.c:1092:2: error: unknown type name 'GstTagDemux'
  return (guint)G_STRUCT_OFFSET (GstTagDemux, element);
  ^

freedesktop-unofficial-mirror/gstreamer__gstreamer-sharp,GStreamer/gstreamer-sharp,GStreamer/gstreamer-sharp,gstreamer-sharp/gstreamer-sharp,gstreamer-sharp/gstreamer-sharp,GStreamer/gstreamer-sharp,gstreamer-sharp/gstreamer-sharp,freedesktop-unofficial-mirror/gstreamer__gstreamer-sharp,freedesktop-unofficial-mirror/gstreamer__gstreamer-sharp