Move av_log() & friends to libavutil

Originally committed as revision 5781 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/log.h

@@ -0,0 +1,37 @@
+#ifndef LOG_H
+#define LOG_H
+
+#include <stdarg.h>
+
+/**
+ * Used by av_log
+ */
+typedef struct AVCLASS AVClass;
+struct AVCLASS {
+    const char* class_name;
+    const char* (*item_name)(void*); /* actually passing a pointer to an AVCodecContext
+                                        or AVFormatContext, which begin with an AVClass.
+                                        Needed because av_log is in libavcodec and has no visibility
+                                        of AVIn/OutputFormat */
+    struct AVOption *option;
+};
+
+/* av_log API */
+
+#define AV_LOG_QUIET -1
+#define AV_LOG_ERROR 0
+#define AV_LOG_INFO 1
+#define AV_LOG_DEBUG 2
+
+#ifdef __GNUC__
+extern void av_log(void*, int level, const char *fmt, ...) __attribute__ ((__format__ (__printf__, 3, 4)));
+#else
+extern void av_log(void*, int level, const char *fmt, ...);
+#endif
+
+extern void av_vlog(void*, int level, const char *fmt, va_list);
+extern int av_log_get_level(void);
+extern void av_log_set_level(int);
+extern void av_log_set_callback(void (*)(void*, int, const char*, va_list));
+
+#endif /* LOG_H */