cleanup library and some basic tests. Includes, add guards to includes
diff --git a/tests/suites/test_suite_hmac_drbg.function b/tests/suites/test_suite_hmac_drbg.function
index bd45112..d58c426 100644
--- a/tests/suites/test_suite_hmac_drbg.function
+++ b/tests/suites/test_suite_hmac_drbg.function
@@ -1,6 +1,8 @@
 /* BEGIN_HEADER */
 #include <polarssl/hmac_drbg.h>
 
+#include <string.h>
+
 typedef struct
 {
     unsigned char *p;