Fix compile error on Linux platform and use c++ style header file(<cstddef> instead of <stddef.h>)

src/media/audio/encode/audio_encoder.cpp

@@ -1,8 +1,7 @@
 #include "audio_encoder.h"
 
-#include <stdlib.h>
-
 #include <chrono>
+#include <cstdlib>
 #include <cstring>
 
 #include "log.h"

src/media/video/decode/video_decoder.h

@@ -7,6 +7,9 @@
 #ifndef _VIDEO_DECODER_H_
 #define _VIDEO_DECODER_H_
 
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
 #include <functional>
 
 #include "video_frame.h"

src/media/video/encode/video_encoder.h

@@ -1,6 +1,9 @@
 #ifndef _VIDEO_ENCODER_H_
 #define _VIDEO_ENCODER_H_
 
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
 #include <functional>
 
 class VideoEncoder {