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/Filelist b/Filelist
index db552d67..22a987c 100644
--- a/Filelist
+++ b/Filelist
@@ -231,6 +231,8 @@
 		src/testdir/silent.wav \
 		src/testdir/popupbounce.vim \
 		src/testdir/crash/* \
+		src/testdir/ru_RU/LC_MESSAGES/Makefile \
+		src/testdir/ru_RU/LC_MESSAGES/__PACKAGE__.po \
 		src/testdir/ru_RU/LC_MESSAGES/__PACKAGE__.mo \
 		src/proto.h \
 		src/protodef.h \