- Added reading of DHM context from memory and file

diff --git a/include/polarssl/md.h b/include/polarssl/md.h
index b23167b..13250dd 100644
--- a/include/polarssl/md.h
+++ b/include/polarssl/md.h
@@ -41,6 +41,8 @@
     POLARSSL_MD_SHA512,
 } md_type_t;
 
+#define POLARSSL_MD_MAX_SIZE         64  /* longest known is SHA512 */
+
 /**
  * Message digest information. Allows message digest functions to be called
  * in a generic way.