libvpx: Pull from upstream

source/libvpx/warnings.h

+/*
+ *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#ifndef WARNINGS_H_
+#define WARNINGS_H_
+
+struct vpx_codec_enc_cfg;
+struct VpxEncoderConfig;
+
+/*
+ * Checks config for improperly used settings. Warns user upon encountering
+ * settings that will lead to poor output quality. Prompts user to continue
+ * when warnings are issued.
+ */
+void check_encoder_config(int disable_prompt,
+                          const struct VpxEncoderConfig *global_config,
+                          const struct vpx_codec_enc_cfg *stream_config);
+
+#endif  // WARNINGS_H_