This patch adds a small hack to get Samba support working on QEMU,
without actually pulling it in as an input.

It seems to work surprisingly well. The only bad thing is that you need
to explicitly install Samba in your profile for Samba support. There's
no error if you try to run something like -net user,smb=/tmp without
having Samba installed in your profile. QEMU will just merrily keep on
running while not actually starting a Samba server.

I've also updated the URL of QEMU.