[glib] Fix compile error in gdbusmessage.c for win64

[Jan-Joost Spanjers <jspanjers src gnome org>]

commit 1011e4269f2c1bb16ad0a72b4b92abaf625c6b56
Author: Hib Eris <hib hiberis nl>
Date:   Sun Mar 31 16:40:34 2013 +0200

    Fix compile error in gdbusmessage.c for win64
    
    https://bugzilla.gnome.org/show_bug.cgi?id=696973

 gio/gdbusmessage.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gio/gdbusmessage.c b/gio/gdbusmessage.c
index cc94375..5464cef 100644
--- a/gio/gdbusmessage.c
+++ b/gio/gdbusmessage.c
@@ -1384,7 +1384,7 @@ read_string (GMemoryBuffer          *mbuf,
                                 "Wanted to read %lu bytes but only got %lu",
                                 (gulong)len),
                                 (gulong)len,
-                   (gulong)mbuf->valid_len - mbuf->pos);
+                   (gulong)(mbuf->valid_len - mbuf->pos));
       mbuf->pos = mbuf->valid_len;
       return NULL;
     }