patch 9.0.0881: cannot get the currently showing mouse shape

Problem:    Cannot get the currently showing mouse shape.
Solution:   Add getmouseshape().
diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index e449003..5a7820e 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -1110,6 +1110,7 @@
 	getcharstr()		get a character from the user as a string
 	getcharmod()		get modifiers for the last typed character
 	getmousepos()		get last known mouse position
+	getmouseshape()		get name of the current mouse shape
 	echoraw()		output characters as-is
 	feedkeys()		put characters in the typeahead queue
 	input()			get a line from the user