qt: use 4.8 branch snapshot for stable on 10.9.

Would be nice if this could be done another way but I think it's better
than making users use --HEAD until Qt fixes their mess (in January):
http://permalink.gmane.org/gmane.comp.lib.qt.devel/13812

Closes #24674.

Signed-off-by: BrewTestBot <brew-test-bot@googlegroups.com>
qt: update bottle.