virtio, pci fixes, enhancements

Most notably this includes virtio cross-endian patches.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

# gpg: Signature made Fri Jun 19 11:18:05 2015 BST using RSA key ID D28D5469
# gpg: Good signature from "Michael S. Tsirkin <mst@kernel.org>"
# gpg:                 aka "Michael S. Tsirkin <mst@redhat.com>"

* remotes/mst/tags/for_upstream:
  vhost: enable vhost without without MSI-X
  pci: Don't register a specialized 'config_write' if default behavior is intended
  hw/core: rebase sysbus_get_fw_dev_path() to g_strdup_printf()
  vhost_net: re-enable when cross endian
  vhost-net: tell tap backend about the vnet endianness
  tap: fix non-linux build
  tap: add VNET_LE/VNET_BE operations
  vhost: set vring endianness for legacy virtio
  virtio: introduce virtio_legacy_is_cross_endian()
  linux-headers: sync vhost.h
  vhost-user: part of virtio

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>