package/qemu: bump version

Bump QEMU to 1.2.1.

Note: 1.3.0 is out now, but ./configure has changed a bit, and there are
new dependencies, so the bump to 1.3.0 is postponed for a litle while...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Francois Perrad <fperrad@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>