cleanup library and some basic tests. Includes, add guards to includes
diff --git a/library/dhm.c b/library/dhm.c
index fb7826a..5861f94 100644
--- a/library/dhm.c
+++ b/library/dhm.c
@@ -35,6 +35,8 @@
 
 #include "polarssl/dhm.h"
 
+#include <string.h>
+
 #if defined(POLARSSL_PEM_PARSE_C)
 #include "polarssl/pem.h"
 #endif