cleanup library and some basic tests. Includes, add guards to includes
diff --git a/include/polarssl/bignum.h b/include/polarssl/bignum.h
index 8ffd562..9e4e05b 100644
--- a/include/polarssl/bignum.h
+++ b/include/polarssl/bignum.h
@@ -24,14 +24,14 @@
#ifndef POLARSSL_BIGNUM_H
#define POLARSSL_BIGNUM_H
-#include <string.h>
-
#if !defined(POLARSSL_CONFIG_FILE)
#include "config.h"
#else
#include POLARSSL_CONFIG_FILE
#endif
+#include <stddef.h>
+
#if defined(POLARSSL_FS_IO)
#include <stdio.h>
#endif