cleanup library and some basic tests. Includes, add guards to includes
diff --git a/tests/suites/test_suite_ctr_drbg.function b/tests/suites/test_suite_ctr_drbg.function
index a36bab2..c9cb22e 100644
--- a/tests/suites/test_suite_ctr_drbg.function
+++ b/tests/suites/test_suite_ctr_drbg.function
@@ -1,6 +1,8 @@
 /* BEGIN_HEADER */
 #include <polarssl/ctr_drbg.h>
 
+#include <string.h>
+
 int test_offset_idx;
 int entropy_func( void *data, unsigned char *buf, size_t len )
 {