patch 8.2.2077: build failure with small features

Problem:    Build failure with small features.
Solution:   Add #ifdef.
diff --git a/src/structs.h b/src/structs.h
index b18134a..631881f 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -4155,7 +4155,9 @@
     int		save_finish_op;
     int		save_opcount;
     int		save_reg_executing;
+#ifdef FEAT_EVAL
     int		save_script_version;
+#endif
     tasave_T	tabuf;
 } save_state_T;