patch 8.1.1364: design for popup window support needs more details

Problem:    Design for popup window support needs more details.
Solution:   Add details about using a window and buffer.  Rename popup_show()
            to popup_create() and add popup_show() and popup_hide().

src/version.c

@@ -767,6 +767,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1364,
 /**/
     1363,
 /**/