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>

runtime/doc/builtin.txt

@@ -416,6 +416,8 @@ mkdir({name} [, {flags} [, {prot}]])
 mode([{expr}])			String	current editing mode
 mzeval({expr})			any	evaluate |MzScheme| expression
 nextnonblank({lnum})		Number	line nr of non-blank line >= {lnum}
+ngettext({single}, {plural}, {number}[, {domain}])
+				String	translate text based on {number}
 nr2char({expr} [, {utf8}])	String	single char with ASCII/UTF-8 value {expr}
 or({expr}, {expr})		Number	bitwise OR
 pathshorten({expr} [, {len}])	String	shorten directory names in a path
@@ -7687,6 +7689,20 @@ nextnonblank({lnum})					*nextnonblank()*
 		Return type: |Number|
 
 
+ngettext({single}, {plural}, {number}[, {domain})	*ngettext()*
+		Return a string that contains the correct value for a
+		message based on the rules for plural form(s) in
+		a language. Examples: >
+			ngettext("File", "Files", 2)  # returns "Files"
+<
+		Can be used as a |method|: >
+			1->ngettext("File", "Files")  # returns "File"
+<
+		See |gettext()| for information on the domain parameter.
+
+		Return type: |String|
+
+
 nr2char({expr} [, {utf8}])				*nr2char()*
 		Return a string with a single character, which has the number
 		value {expr}.  Examples: >

runtime/doc/tags

@@ -9260,6 +9260,7 @@ new-vimscript-8.2	version8.txt	/*new-vimscript-8.2*
 new-virtedit	version6.txt	/*new-virtedit*
 news	intro.txt	/*news*
 nextnonblank()	builtin.txt	/*nextnonblank()*
+ngettext()	builtin.txt	/*ngettext()*
 no-eval-feature	eval.txt	/*no-eval-feature*
 no-type-checking	eval.txt	/*no-type-checking*
 no_buffers_menu	gui.txt	/*no_buffers_menu*

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 @@ String manipulation:					*string-functions*
 	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
 

runtime/doc/version9.txt

@@ -41660,6 +41660,7 @@ Functions: ~
 			Channel or Blob variable
 |matchbufline()|	all the matches of a pattern in a buffer
 |matchstrlist()|	all the matches of a pattern in a List of strings
+|ngettext()|		lookup single/plural message translation
 |popup_setbuf()|	switch to a different buffer in a popup
 |str2blob()|		convert a List of strings into a blob