Update public FFmpeg header files from r16647 to r18286.

third_party/ffmpeg/include/libavutil/base64.h

Index: third_party/ffmpeg/include/libavutil/base64.h
diff --git a/third_party/ffmpeg/include/libavutil/base64.h b/third_party/ffmpeg/include/libavutil/base64.h
index 91df541d59c8d4b2810ecfd8828549d5e06e9311..e3152ebbd26e9ec6d33bc12d37ad293722f9a382 100644
--- a/third_party/ffmpeg/include/libavutil/base64.h
+++ b/third_party/ffmpeg/include/libavutil/base64.h
@@ -1,5 +1,4 @@
 /*
- * Base64.c
  * Copyright (c) 2006 Ryan Martell. (rdm4@martellventures.com)
  *
  * This file is part of FFmpeg.
@@ -25,16 +24,26 @@
 #include <stdint.h>
 
 /**
- * decodes base64
- * param order as strncpy()
+ * Decodes the base64-encoded string in \p in and puts the decoded
+ * data in \p out.
+ *
+ * @param out_size size in bytes of the \p out buffer, it should be at
+ * least 3/4 of the length of \p in
+ * @return the number of bytes written, or a negative value in case of
+ * error
  */
-int av_base64_decode(uint8_t * out, const char *in, int out_length);
+int av_base64_decode(uint8_t *out, const char *in, int out_size);
 
 /**
- * encodes base64
- * @param src data, not a string
- * @param buf output string
+ * Encodes in base64 the data in \p in and puts the resulting string
+ * in \p out.
+ *
+ * @param out_size size in bytes of the \p out string, it should be at
+ * least ((\p in_size + 2) / 3) * 4 + 1
+ * @param in_size size in bytes of the \p in buffer
+ * @return the string containing the encoded data, or NULL in case of
+ * error
  */
-char *av_base64_encode(char * buf, int buf_len, const uint8_t * src, int len);
+char *av_base64_encode(char *out, int out_size, const uint8_t *in, int in_size);
 
 #endif /* AVUTIL_BASE64_H */