ui/gtk: Fix build with older versions of gtk

GDK_KEY_Delete is only defined with gtk version 2.22 and newer,
on older versions this key was called GDK_Delete instead.
Since this is the case for all GDK_KEY_* defines, change the
already existing preprocessor check there to test for version 2.22,
so we know that we can remove this code block in case we require
that version as a minimum one day.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 1478081328-25515-1-git-send-email-thuth@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

ui/gtk.c

@@ -94,7 +94,7 @@
 #define GDK_IS_WIN32_DISPLAY(dpy) (dpy == dpy)
 #endif
 
-#ifndef GDK_KEY_0
+#if !GTK_CHECK_VERSION(2, 22, 0)
 #define GDK_KEY_0 GDK_0
 #define GDK_KEY_1 GDK_1
 #define GDK_KEY_2 GDK_2
@@ -104,6 +104,7 @@
 #define GDK_KEY_plus GDK_plus
 #define GDK_KEY_minus GDK_minus
 #define GDK_KEY_Pause GDK_Pause
+#define GDK_KEY_Delete GDK_Delete
 #endif
 
 /* Some older mingw versions lack this constant or have