avoid warning ('const' discarded)

crypto/engine/enginetest.c

diff --git a/crypto/engine/enginetest.c b/crypto/engine/enginetest.c
index 92cc0da..351b0c7 100644
--- a/crypto/engine/enginetest.c
+++ b/crypto/engine/enginetest.c
@@ -234,8 +234,8 @@
 		}
 	for(loop = 0; loop < 512; loop++)
 		{
-		OPENSSL_free(ENGINE_get_id(block[loop]));
-		OPENSSL_free(ENGINE_get_name(block[loop]));
+		OPENSSL_free((void *)ENGINE_get_id(block[loop]));
+		OPENSSL_free((void *)ENGINE_get_name(block[loop]));
 		}
 	printf("\nTests completed happily\n");
 	to_return = 0;