[glib/benzea/mark-g-source-func] gmain: Mark G_SOURCE_FUNC as available in 2.58

[Benjamin Berg <bberg src gnome org>]

commit 3b039ab181cd1a939df1151362e1571ad140e0f6
Author: Benjamin Berg <bberg redhat com>
Date:   Wed Jan 15 16:52:25 2020 +0100

    gmain: Mark G_SOURCE_FUNC as available in 2.58
    
    This means that GLib will generate appropriate deprecation warnings if
    `GLIB_VERSION_MAX_ALLOWED` has been set to target a GLib version older
    than 2.58.

 glib/gmain.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/glib/gmain.h b/glib/gmain.h
index 49f30651c..d4776c19b 100644
--- a/glib/gmain.h
+++ b/glib/gmain.h
@@ -188,7 +188,7 @@ typedef gboolean (*GSourceFunc)       (gpointer user_data);
  *
  * Since: 2.58
  */
-#define G_SOURCE_FUNC(f) ((GSourceFunc) (void (*)(void)) (f))
+#define G_SOURCE_FUNC(f) ((GSourceFunc) (void (*)(void)) (f)) GLIB_AVAILABLE_MACRO_IN_2_58
 
 /**
  * GChildWatchFunc: