Add support for flac in ogg container

Signed-off-by: Mahyar Koshkouei <deltabeard@users.noreply.github.com>

source/flac.h

@@ -41,3 +41,11 @@ uint64_t decodeFlac(void* buffer);
  * Free Flac decoder.
  */
 void exitFlac(void);
+
+/**
+ * Checks if the input file is Flac
+ *
+ * \param in	Input file.
+ * \return		0 if Flac file, else not or failure.
+ */
+int isFlac(const char* in);