patch 8.2.3718: compiler warns for unused variable without +textprop

Problem:    Compiler warns for unused variable without the +textprop feature.
            (John Marriott)
Solution:   Adjust #ifdefs.
diff --git a/src/version.c b/src/version.c
index c5e5f6b..cf8f945 100644
--- a/src/version.c
+++ b/src/version.c
@@ -754,6 +754,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3718,
+/**/
     3717,
 /**/
     3716,