patch 8.2.3109: check for $DISPLAY never fails

Problem:    Check for $DISPLAY never fails.
Solution:   Use eval().

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3109,
 /**/
     3108,
 /**/