RFC qemu/vhost-net: mergeable buffers support

This adds mergeable buffers support in vhost-net in qemu. With this patch, sending raw packets while vhost-net is active should work as well: important for migration. Compile-tested only for now. David, could you please review and maybe try this out?
The kernel side is in vhost-net-next. I intend for it to got into net-next and then into 2.6.36.

TODO: basic test. migration test, send pull request.

Michael S. Tsirkin (3):
tap: generalize code for different vnet header len
tap: add APIs for vnet header length
vhost_net: mergeable buffers support

 hw/vhost_net.c    |   23 ++++++++++++++++++++++-
 net/tap-aix.c     |    9 +++++++++
 net/tap-bsd.c     |    9 +++++++++
 net/tap-linux.c   |   29 +++++++++++++++++++++++++++++
 net/tap-linux.h   |    8 ++++++++
 net/tap-solaris.c |    9 +++++++++
 net/tap-win32.c   |    9 +++++++++
 net/tap.c         |   49 +++++++++++++++++++++++++++++++++++--------------
 net/tap.h         |    4 ++++
 9 files changed, 134 insertions(+), 15 deletions(-)

MST