runtime: set 'cpoptions' for line-continuation in various runtime files

closes: #17121

Signed-off-by: Eisuke Kawashima <e-kwsm@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/ftplugin/mediawiki.vim b/runtime/ftplugin/mediawiki.vim
index 4618246..399de42 100644
--- a/runtime/ftplugin/mediawiki.vim
+++ b/runtime/ftplugin/mediawiki.vim
@@ -3,6 +3,7 @@
 " Home: http://en.wikipedia.org/wiki/Wikipedia:Text_editor_support#Vim
 " Last Change: 2024 Jul 14
 " Credits: chikamichi
+" 2025 Apr 16 by Vim Project (set 'cpoptions' for line continuation, #17121)
 "
 
 if exists("b:did_ftplugin")
@@ -10,6 +11,9 @@
 endif
 let b:did_ftplugin = 1
 
+let s:cpo_save = &cpo
+set cpo&vim
+
 " Many MediaWiki wikis prefer line breaks only at the end of paragraphs
 " (like in a text processor), which results in long, wrapping lines.
 setlocal wrap linebreak
@@ -40,3 +44,6 @@
 
 let b:undo_ftplugin = "setl commentstring< comments< formatoptions< foldexpr< foldmethod<"
 let b:undo_ftplugin += " matchpairs< linebreak< wrap< textwidth<"
+
+let &cpo = s:cpo_save
+unlet s:cpo_save