patch 8.2.4160: cannot change the register used for Select mode delete

Problem:    Cannot change the register used for Select mode delete.
Solution:   Make CTRL-R set the register to be used when deleting text for
            Select mode. (Shougo Matsushita, closes #9531)
diff --git a/src/globals.h b/src/globals.h
index 7e0c1e5..2f6a4b4 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -875,6 +875,8 @@
 				// whether Visual mode is active
 EXTERN int	VIsual_select INIT(= FALSE);
 				// whether Select mode is active
+EXTERN int	VIsual_select_reg INIT(= 0);
+				// register name for Select mode
 EXTERN int	restart_VIsual_select INIT(= 0);
 				// restart Select mode when next cmd finished
 EXTERN int	VIsual_reselect;