patch 8.1.1429: "pos" option of popup window not supported yet

Problem:    "pos" option of popup window not supported yet.
Solution:   Implement the option. Rename popup_getposition() to
            popup_getpos().

src/version.c

@@ -767,6 +767,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1429,
 /**/
     1428,
 /**/