- Added Doxygen source code documentation parts (donated by Fox-IT)

diff --git a/include/polarssl/md4.h b/include/polarssl/md4.h
index 84f8b1f..c3c5d7e 100644
--- a/include/polarssl/md4.h
+++ b/include/polarssl/md4.h
@@ -1,6 +1,8 @@
 /**
  * \file md4.h
  *
+ * \brief MD4 message digest algorithm (hash function)
+ *
  *  Copyright (C) 2006-2010, Brainspark B.V.
  *
  *  This file is part of PolarSSL (http://www.polarssl.org)