tiff: perform minor cleanups in the header

Add link to official specifications, remove author duplication and
others.

libavcodec/tiff.h

 /*
- * TIFF tables
  * Copyright (c) 2006 Konstantin Shishkov
  *
  * This file is part of FFmpeg.
@@ -19,13 +18,16 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#ifndef AVCODEC_TIFF_H
+#define AVCODEC_TIFF_H
+
 /**
- * TIFF tables
  * @file
- * @author Konstantin Shishkov
+ * TIFF tables
+ *
+ * For more information about the TIFF format, check the official docs at:
+ * http://partners.adobe.com/public/developer/tiff/index.html
  */
-#ifndef AVCODEC_TIFF_H
-#define AVCODEC_TIFF_H
 
 #include <stdint.h>