threads: add CODEC_CAP_AUTO_THREADS for libvpx and xavs

libavcodec/libvpxdec.c

@@ -119,5 +119,6 @@ AVCodec ff_libvpx_decoder = {
     .init           = vp8_init,
     .close          = vp8_free,
     .decode         = vp8_decode,
-    .long_name = NULL_IF_CONFIG_SMALL("libvpx VP8"),
+    .capabilities   = CODEC_CAP_AUTO_THREADS,
+    .long_name      = NULL_IF_CONFIG_SMALL("libvpx VP8"),
 };

libavcodec/libvpxenc.c

@@ -572,7 +572,7 @@ AVCodec ff_libvpx_encoder = {
     .init           = vp8_init,
     .encode         = vp8_encode,
     .close          = vp8_free,
-    .capabilities   = CODEC_CAP_DELAY,
+    .capabilities   = CODEC_CAP_DELAY | CODEC_CAP_AUTO_THREADS,
     .pix_fmts = (const enum PixelFormat[]){PIX_FMT_YUV420P, PIX_FMT_NONE},
     .long_name = NULL_IF_CONFIG_SMALL("libvpx VP8"),
     .priv_class = &class,

libavcodec/libxavs.c

@@ -414,7 +414,7 @@ AVCodec ff_libxavs_encoder = {
     .init           = XAVS_init,
     .encode         = XAVS_frame,
     .close          = XAVS_close,
-    .capabilities   = CODEC_CAP_DELAY,
+    .capabilities   = CODEC_CAP_DELAY | CODEC_CAP_AUTO_THREADS,
     .pix_fmts       = (const enum PixelFormat[]) { PIX_FMT_YUV420P, PIX_FMT_NONE },
     .long_name      = NULL_IF_CONFIG_SMALL("libxavs - the Chinese Audio Video Standard Encoder"),
     .priv_class     = &class,