Replace dprintf with av_dlog

dprintf clashes with POSIX.1-2008
(cherry picked from commit dfd2a005eb)

libavutil/internal.h

@@ -114,13 +114,6 @@
 
 /* debug stuff */
 
-/* dprintf macros */
-#ifdef DEBUG
-#    define dprintf(pctx, ...) av_log(pctx, AV_LOG_DEBUG, __VA_ARGS__)
-#else
-#    define dprintf(pctx, ...)
-#endif
-
 #define av_abort()      do { av_log(NULL, AV_LOG_ERROR, "Abort at %s:%d\n", __FILE__, __LINE__); abort(); } while (0)
 
 /* math */

libavutil/log.h

@@ -135,6 +135,17 @@ void av_log_set_callback(void (*)(void*, int, const char*, va_list));
 void av_log_default_callback(void* ptr, int level, const char* fmt, va_list vl);
 const char* av_default_item_name(void* ctx);
 
+/**
+ * av_dlog macros
+ * Useful to print debug messages that shouldn't get compiled in normally.
+ */
+
+#ifdef DEBUG
+#    define av_dlog(pctx, ...) av_log(pctx, AV_LOG_DEBUG, __VA_ARGS__)
+#else
+#    define av_dlog(pctx, ...)
+#endif
+
 /**
  * Skip repeated messages, this requires the user app to use av_log() instead of
  * (f)printf as the 2 would otherwise interfere and lead to