ftplugin(gdb): add matchit support

closes: #14462

Signed-off-by: Wu, Zhenyu <wuzhenyu@ustc.edu>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/ftplugin/gdb.vim b/runtime/ftplugin/gdb.vim
index 2473b13..7c10633 100644
--- a/runtime/ftplugin/gdb.vim
+++ b/runtime/ftplugin/gdb.vim
@@ -1,12 +1,20 @@
 " Vim filetype plugin file
 " Language:	gdb
 " Maintainer:	Michaël Peeters <NOSPAMm.vim@noekeon.org>
-" Last Changed: 26 Oct 2017
+" Last Changed: 2017-10-26
+"               2024-04-10:	- add Matchit support (by Vim Project)
 
 if exists("b:did_ftplugin") | finish | endif
 let b:did_ftplugin = 1
 
 setlocal commentstring=#%s
+setlocal include=^\\s*source
 
 " Undo the stuff we changed.
-let b:undo_ftplugin = "setlocal cms<"
+let b:undo_ftplugin = "setlocal cms< include<"
+
+" Matchit support
+if !exists('b:match_words')
+  let b:match_words = '\<\%(if\|while\|define\|document\)\>:\<else\>:\<end\>'
+  let b:undo_ftplugin ..= " | unlet! b:match_words"
+endif