patch 9.0.1799: Russian menu translation can be improved

Problem:  Russian menu translation can be improved
Solution: update the Russian menu files

closes: #12903

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: RestorerZ <restorer@mail2k.ru>
diff --git a/runtime/lang/menu_ru_ru.vim b/runtime/lang/menu_ru_ru.vim
index b5e4b79..17bf0a4 100644
--- a/runtime/lang/menu_ru_ru.vim
+++ b/runtime/lang/menu_ru_ru.vim
@@ -1,3 +1,14 @@
 " Menu Translations:	Russian
 
-source <sfile>:p:h/menu_ru_ru.utf-8.vim
+if ('utf-8' ==? &enc) && filereadable(expand('<sfile>:p:h') . '/menu_ru_ru.utf-8.vim')
+    source <sfile>:p:h/menu_ru_ru.utf-8.vim
+elseif ('cp1251' ==? &enc) && filereadable(expand('<sfile>:p:h') . '/menu_ru_ru.cp1251.vim')
+    source <sfile>:p:h/menu_ru_ru.cp1251.vim
+" elseif ('cp866' ==? &enc) && filereadable(expand('<sfile>:p:h') . '/menu_ru_ru.cp866.vim')
+"    source <sfile>:p:h/menu_ru_ru.cp866.vim
+elseif ('koi8-r' ==? &enc) && filereadable(expand('<sfile>:p:h') . '/menu_ru_ru.koi8-r.vim')
+    source <sfile>:p:h/menu_ru_ru.koi8-r.vim
+else
+    echomsg 'Could not find the menu file matching the current encoding'
+endif
+