patch 8.2.5066: timer_create is not available on every Mac system

Problem:    Timer_create is not available on every Mac system. (Hisashi T
            Fujinaka)
Solution:   Adjust #ifdef.
diff --git a/src/structs.h b/src/structs.h
index 4666d02..58152b9 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -3411,6 +3411,7 @@
     int		trail;
     int		lead;
     int		*multispace;
+    int		*leadmultispace;
 #ifdef FEAT_CONCEAL
     int		conceal;
 #endif