bump(app-emulation/qemu): sync with upstream

There is a bug in 1.2 that was causing qemu to eat massive amounts of
ram. Hopefully latest stable (1.4) or 1.5 doesn't do that. Bumping some
dependencies along with qemu as well.

Packages updated:
  app-emulation/qemu
  sys-firmware/ipxe
  sys-firmware/seabios
  x11-libs/pixman