lua: export variables module to lua demuxer

modules/lua/demux.c

@@ -151,6 +151,7 @@ static int probe_luascript( vlc_object_t *p_this, const char * psz_filename,
     luaopen_msg( L );
     luaopen_strings( L );
     luaopen_stream( L );
+    luaopen_variables( L );
     luaopen_xml( L );
     luaopen_md5( L );
     lua_pushstring( L, p_demux->psz_location );