patch 8.2.0924: cannot save and restore a register properly

Problem:    Cannot save and restore a register properly.
Solution:   Add getreginfo() and make setreg() accept a dictionary. (Andy
            Massimino, closes #3370)
diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index 89d25df..1d896f9 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -1155,6 +1155,7 @@
 	undotree()		return the state of the undo tree
 
 	getreg()		get contents of a register
+	getreginfo()		get information about a register
 	getregtype()		get type of a register
 	setreg()		set contents and type of a register
 	reg_executing()		return the name of the register being executed