Ticket #2540 Enable threading when using -c:v libx264rgb

Signed-off-by: Gunther Piez <gupiez@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/libx264.c

@@ -743,7 +743,7 @@ AVCodec ff_libx264rgb_encoder = {
     .init           = X264_init,
     .encode2        = X264_frame,
     .close          = X264_close,
-    .capabilities   = CODEC_CAP_DELAY,
+    .capabilities   = CODEC_CAP_DELAY | CODEC_CAP_AUTO_THREADS,
     .long_name      = NULL_IF_CONFIG_SMALL("libx264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 RGB"),
     .priv_class     = &rgbclass,
     .defaults       = x264_defaults,