Fix name conflict and implicit use of functions from string.h
diff --git a/tests/suites/test_suite_ctr_drbg.function b/tests/suites/test_suite_ctr_drbg.function
index d8ffebe..73f63b9 100644
--- a/tests/suites/test_suite_ctr_drbg.function
+++ b/tests/suites/test_suite_ctr_drbg.function
@@ -1,5 +1,6 @@
 /* BEGIN_HEADER */
 #include "mbedtls/ctr_drbg.h"
+#include "string.h"
 
 static int test_offset_idx;
 static int mbedtls_test_entropy_func( void *data, unsigned char *buf, size_t len )