patch 8.1.1811: popup window color cannot be set to "Normal"

Problem:    Popup window color cannot be set to "Normal".
Solution:   Check for non-empty 'wincolor' instead of zero attribute.
            (closes #4772)

src/version.c

@@ -773,6 +773,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1811,
 /**/
     1810,
 /**/