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/runtime/doc/visual.txt b/runtime/doc/visual.txt
index 460cf5a..eed1023 100644
--- a/runtime/doc/visual.txt
+++ b/runtime/doc/visual.txt
@@ -488,6 +488,11 @@
 - ESC stops Select mode.
 - CTRL-O switches to Visual mode for the duration of one command. *v_CTRL-O*
 - CTRL-G switches to Visual mode.
+- CTRL-R {register} selects the register to be used for the text that is
+  deleted when typing text.					  *v_CTRL-R*
+  Unless you specify the "_" (black hole) register, the unnamed register is
+  also overwritten.
+
 
 Otherwise, typed characters are handled as in Visual mode.