patch 8.1.2170: cannot build without the +termresponse feature

Problem:    Cannot build without the +termresponse feature.
Solution:   Add #ifdef.
diff --git a/src/version.c b/src/version.c
index 78d0dc9..b7d9cb7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -754,6 +754,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2170,
+/**/
     2169,
 /**/
     2168,