patch 8.1.0334: 'autowrite' takes effect when buffer is not to be written

Problem:    'autowrite' takes effect when buffer is not to be written.
Solution:   Don't write buffers that are not supposed to be written. (Even Q
            Jones, closes #3391)  Add tests for 'autowrite'.

src/version.c

@@ -794,6 +794,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    334,
 /**/
     333,
 /**/