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)
diff --git a/src/version.c b/src/version.c
index 6904482..32759b1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -774,6 +774,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1811,
+/**/
     1810,
 /**/
     1809,