patch 9.0.1483: += operator does not work on class member

Problem:    += operator does not work on class member.
Solution:   Do not skip as if "this." was used. (Christian Brabandt,
            closes #12263)

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1483,
 /**/
     1482,
 /**/