The plugin description is not supposed to be a string constant, but an
unescaped string, to be concatenated with function names.

This used to be acceptable (though would have warned), but breaks with
the GStreamer 1.13 development branch.

rb-fm-radio-gst-src.c:181:6: error: pasting ""rbsilencesrc"" and "_get_desc" does not give a valid preprocessing token
      "rbsilencesrc",
      ^

https://bugzilla.gnome.org/show_bug.cgi?id=788706