patch 8.0.0972: compiler warnings for unused variables

Problem:    Compiler warnings for unused variables. (Tony Mechelynck)
Solution:   Add #ifdefs.
diff --git a/src/version.c b/src/version.c
index 9f9b8ab..cf72cb8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    972,
+/**/
     971,
 /**/
     970,