Update bugzilla link

There are several "http://bugzilla.gnome.org" link in files.

glade.doap : http://bugzilla.gnome.org/browse.cgi?product=glade
configure.ag : [http://bugzilla.gnome.org/enter_bug.cgi?product=glade],
glade.nsi.in : !define HELPURL "http://bugzilla.gnome.org/browse.cgi?product=glade"