Fix name conflict and implicit use of functions from string.h
diff --git a/tests/suites/test_suite_entropy.function b/tests/suites/test_suite_entropy.function
index 2bab796..9930c03 100644
--- a/tests/suites/test_suite_entropy.function
+++ b/tests/suites/test_suite_entropy.function
@@ -1,6 +1,7 @@
 /* BEGIN_HEADER */
 #include "mbedtls/entropy.h"
 #include "mbedtls/entropy_poll.h"
+#include "string.h"
 
 /*
  * Number of calls made to entropy_dummy_source()