minor improvements

[skip ci]

tests/test.c

@@ -392,7 +392,7 @@ int main(int argc, char **argv)
          nop++;
       }
       else {
-         printf("failed %10.3fms", (double)(delta)/1000);
+         printf("failed (%s) %10.3fms", error_to_string(x), (double)(delta)/1000);
          fail++;
       }
    }

tests/tomcrypt_test.h

@@ -29,7 +29,7 @@
  * this and so it's treated as an error and you have to comment out the
  * following statement :)
  */
-#error EXT_MATH_LIB is required to be defined
+#error One of USE_LTM, USE_TFM, USE_GMP and EXT_MATH_LIB is required to be defined
 #endif
 #endif