[libgnomekbd] gkbd-keyboard-display: include string.h to avoid the inplicite defination warning in build.

[Corentin Noël <corentinnoel src gnome org>]

commit c9746f249b2345dd699c2ec318ebc2799f4b83e2
Author: zhaoqiang <zhaoqiang gnome org>
Date:   Thu Jun 3 21:35:21 2021 +0800

    gkbd-keyboard-display: include string.h to avoid the inplicite defination warning in build.

 libgnomekbd/gkbd-keyboard-display.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/libgnomekbd/gkbd-keyboard-display.c b/libgnomekbd/gkbd-keyboard-display.c
index 3e2f271..5b1476c 100644
--- a/libgnomekbd/gkbd-keyboard-display.c
+++ b/libgnomekbd/gkbd-keyboard-display.c
@@ -18,6 +18,7 @@
  */
 
 #include <stdlib.h>
+#include <string.h>
 #include <libintl.h>
 #include <config.h>