GUACAMOLE-638: avcodec_register_all() should be used only if not deprecated.

src/guacenc/guacenc.c

@@ -75,8 +75,10 @@ int main(int argc, char* argv[]) {
     guacenc_log(GUAC_LOG_INFO, "Guacamole video encoder (guacenc) "
             "version " VERSION);
 
+#if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(58, 10, 100)
     /* Prepare libavcodec */
     avcodec_register_all();
+#endif
 
     /* Track number of overall failures */
     int total_files = argc - optind;