qt48: security fix for CVE-2013-0254

Taken from Gentoo.
libv8 still broken in chroots, but this scons patch script fixes it
dbus: attempt to fix build on FreeBSD and Darwin

Also build it there.
vala, libusb1, deps of libjpeg: attempt to fix on non-Linux
qt48, gstreamer: attempt to fix on non-Linux