avcodec/libx264: remove FF_CODEC_CAP_INIT_THREADSAFE flag

Libx264 uses strtok which is not thread safe. Strtok is used in
x264_param_default_preset in param_apply_tune in x264/common/base.c.
Therefore the flag must be removed.

x264 fixed the issue, once the fix is pushed to stable, an #if can be added
to re-enable the flag based on X264_BUILD number.

Fixes ticket #7446.
Signed-off-by: Marton Balint <cus@passwd.hu>
(cherry picked from commit b02490a4)

libavcodec/libx264.c

@@ -1053,8 +1053,7 @@ AVCodec ff_libx264_encoder = {
     .priv_class       = &x264_class,
     .defaults         = x264_defaults,
     .init_static_data = X264_init_static,
-    .caps_internal    = FF_CODEC_CAP_INIT_THREADSAFE |
-                        FF_CODEC_CAP_INIT_CLEANUP,
+    .caps_internal    = FF_CODEC_CAP_INIT_CLEANUP,
     .wrapper_name     = "libx264",
 };
 #endif
@@ -1105,8 +1104,7 @@ AVCodec ff_libx262_encoder = {
     .priv_class       = &X262_class,
     .defaults         = x264_defaults,
     .pix_fmts         = pix_fmts_8bit,
-    .caps_internal    = FF_CODEC_CAP_INIT_THREADSAFE |
-                        FF_CODEC_CAP_INIT_CLEANUP,
+    .caps_internal    = FF_CODEC_CAP_INIT_CLEANUP,
     .wrapper_name     = "libx264",
 };
 #endif