[gnome-terminal] build: Suppress a warning about casting between incompatible function types

[Egmont Koblinger <egmontkob src gnome org>]

commit f664f75b07d35e0771797f806956687e548c4b19
Author: Egmont Koblinger <egmont gmail com>
Date:   Sat Sep 14 22:06:48 2019 +0200

    build: Suppress a warning about casting between incompatible function types
    
    https://gitlab.gnome.org/GNOME/gnome-terminal/issues/96

 src/terminal-util.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/src/terminal-util.c b/src/terminal-util.c
index 72a0d401..66ab7a90 100644
--- a/src/terminal-util.c
+++ b/src/terminal-util.c
@@ -970,7 +970,8 @@ terminal_util_bind_mnemonic_label_sensitivity (GtkWidget *widget)
 
   if (GTK_IS_CONTAINER (widget))
     gtk_container_foreach (GTK_CONTAINER (widget),
-                           (GtkCallback) terminal_util_bind_mnemonic_label_sensitivity,
+                           /* See #96 for double casting. */
+                           (GtkCallback) (GCallback) terminal_util_bind_mnemonic_label_sensitivity,
                            NULL);
 }