gio: Use heap-allocated buffer
gio: Use heap-allocated buffer

As if we were to increase the buffer size, it would be a bit too big to
fit on the stack.

https://bugzilla.gnome.org/show_bug.cgi?id=773823

endlessm/glib,endlessm/glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,johne53/MB3Glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib