patch 9.1.1064: not possible to use plural forms with gettext()

Problem:  not possible to use plural forms with gettext()
Solution: implement ngettext() Vim script function (Christ van Willegen)

closes: #16561

Signed-off-by: Christ van Willegen <cvwillegen@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index 35aba02..0d09fc9 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -1,4 +1,4 @@
-*usr_41.txt*	For Vim version 9.1.  Last change: 2025 Jan 16
+*usr_41.txt*	For Vim version 9.1.  Last change: 2025 Feb 01
 
 		     VIM USER MANUAL - by Bram Moolenaar
 
@@ -801,6 +801,7 @@
 	trim()			trim characters from a string
 	bindtextdomain()	set message lookup translation base path
 	gettext()		lookup message translation
+	ngettext()		lookup single/plural message translation
 	str2blob()		convert a list of strings into a blob
 	blob2str()		convert a blob into a list of strings