patch 8.1.1596: when resizing the screen may draw popup in wrong position

Problem:    When resizing the screen may draw popup in wrong position. (Masato
            Nishihata)
Solution:   Check the popup is not outside of the screen. (fixes #4592)

src/popupwin.c

@@ -2154,8 +2154,9 @@ update_popups(void (*win_update)(win_T *wp))
 	wp->w_winrow += top_off;
 	wp->w_wincol += left_off;
 
-	// Draw the popup text.
-	win_update(wp);
+	// Draw the popup text, unless it's off screen.
+	if (wp->w_winrow < screen_Rows && wp->w_wincol < screen_Columns)
+	    win_update(wp);
 
 	wp->w_winrow -= top_off;
 	wp->w_wincol -= left_off;

src/version.c

@@ -777,6 +777,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1596,
 /**/
     1595,
 /**/