Add a new virNetClientSendNonBlock which returns 2 on
full send, 1 on partial send, 0 on no send, -1 on error

If a partial send occurs, then a subsequent call to any
of the virNetClientSend* APIs will finish any outstanding
I/O.

TODO: the virNetClientEvent event handler could be used
to speed up completion of partial sends if an event loop
is present.

* src/rpc/virnetsocket.h, src/rpc/virnetsocket.c: Add new
  virNetSocketHasPendingData() API to test for cached
  data pending send.
* src/rpc/virnetclient.c, src/rpc/virnetclient.h: Add new
  virNetClientSendNonBlock() API to send non-blocking API

The src/util/network.c file is a dumping ground for many different
APIs. Split it up into 5 pieces, along functional lines

 - src/util/virnetdevbandwidth.c: virNetDevBandwidth type & helper APIs
 - src/util/virnetdevvportprofile.c: virNetDevVPortProfile type & helper APIs
 - src/util/virsocketaddr.c: virSocketAddr and APIs
 - src/conf/netdev_bandwidth_conf.c: XML parsing / formatting
   for virNetDevBandwidth
 - src/conf/netdev_vport_profile_conf.c: XML parsing / formatting
   for virNetDevVPortProfile

* src/util/network.c, src/util/network.h: Split into 5 pieces
* src/conf/netdev_bandwidth_conf.c, src/conf/netdev_bandwidth_conf.h,
  src/conf/netdev_vport_profile_conf.c, src/conf/netdev_vport_profile_conf.h,
  src/util/virnetdevbandwidth.c, src/util/virnetdevbandwidth.h,
  src/util/virnetdevvportprofile.c, src/util/virnetdevvportprofile.h,
  src/util/virsocketaddr.c, src/util/virsocketaddr.h: New pieces
* daemon/libvirtd.h, daemon/remote.c, src/conf/domain_conf.c,
  src/conf/domain_conf.h, src/conf/network_conf.c,
  src/conf/network_conf.h, src/conf/nwfilter_conf.h,
  src/esx/esx_util.h, src/network/bridge_driver.c,
  src/qemu/qemu_conf.c, src/rpc/virnetsocket.c,
  src/rpc/virnetsocket.h, src/util/dnsmasq.h, src/util/interface.h,
  src/util/iptables.h, src/util/macvtap.c, src/util/macvtap.h,
  src/util/virnetdev.h, src/util/virnetdevtap.c,
  tools/virsh.c: Update include files

The code calling sendfd/recvfd was mistakenly assuming those
calls would never block. They can in fact return EAGAIN and
this is causing us to drop the client connection when blocking
ocurrs while sending/receiving FDs.

Fixing this is a little hairy on the incoming side, since at
the point where we see the EAGAIN, we already thought we had
finished receiving all data for the packet. So we play a little
trick to reset bufferOffset again and go back into polling for
more data.

* src/rpc/virnetsocket.c, src/rpc/virnetsocket.h: Update
  virNetSocketSendFD/RecvFD to return 0 on EAGAIN, or 1
  on success
* src/rpc/virnetclient.c: Move decoding of header & fds
  out of virNetClientCallDispatch and into virNetClientIOHandleInput.
  Handling blocking when sending/receiving FDs
* src/rpc/virnetmessage.h: Add a 'donefds' field to track
  how many FDs we've sent / received
* src/rpc/virnetserverclient.c: Handling blocking when
  sending/receiving FDs

Add APIs to the virNetSocket object, to allow file descriptors
to be sent/received over UNIX domain socket connections

* src/rpc/virnetsocket.c, src/rpc/virnetsocket.h,
  src/libvirt_private.syms: Add APIs for FD send/recv

Instead of directly manipulating sock->refs, add a virSocketRef
API

* src/rpc/virnetsocket.c, src/rpc/virnetsocket.h: Add virSocketRef

This patch allows owner's UID to be changed as well.

So that callers can change the default value.

* src/rpc/virnetsocket.c, src/rpc/virnetsocket.h: Add
  virNetSocketDupFD()
* src/rpc/virnetclient.c, src/rpc/virnetclient.h: Add
  virNetClientDupFD() and virNetClientGetFD()

This patch introduces a internal RPC API "virNetServerClose", which
is standalone with "virNetServerFree".  it closes all the socket fds,
and unlinks the unix socket paths, regardless of whether the socket
is still referenced or not.

This is to address regression bug:
https://bugzilla.redhat.com/show_bug.cgi?id=725702

New optional parameter "keyfile" for ssh transport allows the user to select
the private key to be used to authenticate to the remote host.

When unregistering an I/O callback from a virNetSocket object,
there is still a chance that an event may come in on the callback.
In this case it is possible that the virNetSocket might have been
freed already. Make use of a virFreeCallback when registering
the I/O callbacks and hold a reference for the entire time the
callback is set.

* src/rpc/virnetsocket.c: Register a free function for the
  file handle watch
* src/rpc/virnetsocket.h, src/rpc/virnetserverservice.c,
  src/rpc/virnetserverclient.c, src/rpc/virnetclient.c: Add
  a free function for the socket I/O watches

Set StrictHostKeyChecking=no to auto-accept new ssh host keys if the
no_verify extra parameter was specified.  This won't disable host key
checking for already known hosts.  Includes a test and documentation.

Allow RPC servers to advertise themselves using MDNS,
via Avahi

* src/rpc/virnetserver.c, src/rpc/virnetserver.h: Allow
  registration of MDNS services via avahi
* src/rpc/virnetserverservice.c, src/rpc/virnetserverservice.h: Add
  API to fetch the listen port number
* src/rpc/virnetsocket.c, src/rpc/virnetsocket.h: Add API to
  fetch the local port number
* src/rpc/virnetservermdns.c, src/rpc/virnetservermdns.h: Represent
  an MDNS advertisement

This extends the basic virNetSocket APIs to allow them to have
a handle to the TLS/SASL session objects, once established.
This ensures that any data reads/writes are automagically
passed through the TLS/SASL encryption layers if required.

* src/rpc/virnetsocket.c, src/rpc/virnetsocket.h: Wire up
  SASL/TLS encryption

Introduces a simple wrapper around the raw POSIX sockets APIs
and name resolution APIs. Allows for easy creation of client
and server sockets with correct usage of name resolution APIs
for protocol agnostic socket setup.

It can listen for UNIX and TCP stream sockets.

It can connect to UNIX, TCP streams directly, or indirectly
to UNIX sockets via an SSH tunnel or external command

* src/Makefile.am: Add to libvirt-net-rpc.la
* src/rpc/virnetsocket.c, src/rpc/virnetsocket.h: Generic
  sockets APIs
* tests/Makefile.am: Add socket test
* tests/virnetsockettest.c: New test case
* tests/testutils.c: Avoid overriding LIBVIRT_DEBUG settings
* tests/ssh.c: Dumb helper program for SSH tunnelling tests