[gtk+] wayland: Annotate the log_handler function

[Emmanuele Bassi <ebassi src gnome org>]

commit 2a4f07ed9f7429f26c6e7f0b63c159186a6c9221
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Fri Apr 28 23:10:51 2017 +0100

    wayland: Annotate the log_handler function
    
    The log_handler() internal function is a candidate for the GCC format
    attribute for printf-like functions.

 gdk/wayland/gdkdisplay-wayland.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/gdk/wayland/gdkdisplay-wayland.c b/gdk/wayland/gdkdisplay-wayland.c
index 4780546..bb1b78a 100644
--- a/gdk/wayland/gdkdisplay-wayland.c
+++ b/gdk/wayland/gdkdisplay-wayland.c
@@ -481,6 +481,7 @@ static const struct wl_registry_listener registry_listener = {
     gdk_registry_handle_global_remove
 };
 
+G_GNUC_PRINTF (1, 0)
 static void
 log_handler (const char *format, va_list args)
 {