[ext deps] Update xulrunner to 1.9.2 for GNOME 3.0

[Luca Ferretti <lferrett gnome org>]

Hi,

it seems we have to increase the minimum required xulrunner version from
1.9.1 to 1.9.2. This update is needed in order to build gjs (and so
gnome-shell).

In order to provide a complete information about it, please note: 
      * we need to tune jhbuild module to 1.9.2, a preliminary patch is
        available here https://bugzilla.gnome.org/show_bug.cgi?id=634953
        If you have more info or if you want to test it on other systems
        (I'm on ubuntu 10.10 by now) you are welcome. 
      * it seems that mozilla no longer provides sources for older
        xulrunner releases; i.e. the previous patch will download and
        hopefully build xulrunner 1.9.2.12, but when mozilla will
        release 1.9.2.13, that package will no longer available; if you
        have more info about it (i.e. a safe and reliable place to
        download) let us known. Otherwise be ready to update jhbuild :) 

Cheers, Luca