It is useful to know where the client is connecting from,
so include the socket address in probe data.

* daemon/libvirtd.h: Use virSocketAddr for storing client
  address and keep printable address handy for logging
* daemon/libvirtd.c: Include socket address in client
  connect/disconnect probes
* daemon/probes.d: Add socket address to probes
* examples/systemtap/client.stp: Print socket address
* src/util/network.h: Add sockaddr_un to virSocketAddr union

The getnameinfo() function is more flexible than inet_ntop()
avoiding the need to if/else the code based on socket family.
Also make it support UNIX socket addrs and allow inclusion
of a port (service) address. Finally do proper error reporting
via normal APIs.

* src/conf/domain_conf.c, src/nwfilter/nwfilter_ebiptables_driver.c,
  src/qemu/qemu_conf.c: Fix error handling with virSocketFormat
* src/util/network.c: Rewrite virSocketFormat to use getnameinfo
  and cope with UNIX socket addrs.

Some operations on socket addresses need to know the length of
the sockaddr struct for the particular address family. This
info was being discarded when passing around virSocketAddr
instances. Turn it from a union into a struct containing
union+socklen_t fields, so length is always kept around.

* src/util/network.h: Add socklen_t field to virSocketAddr
* src/util/network.c, src/network/bridge_driver.c,
  src/conf/domain_conf.c: Update to take account of new
  struct definition.

This patch changes the network filtering code to use libvirt's existing
IPv4 and IPv6 address parsers/printers rather than my self-written ones.

I am introducing a new function in network.c that counts the number of
bits in a netmask and ensures that the given address is indeed a netmask,
return -1 on error or values of 0-32 for IPv4 addresses and 0-128 for
IPv6 addresses. I then based the function checking for valid netmask
on invoking this function.

* global: patch created by running:
for f in $(git ls-files '*.[ch]') ; do
    cppi $f > $f.t && mv $f.t $f
done

MinGW's ld gives an error when trying to export undefined symbols.

* src/util/network.[ch] Add functions for address->text and get/set
  port number
* src/libvirt_private.syms: add new entry points

* src/util/network.h src/util/network.c: utilities to parse network
  addresses, check netmask and compute ranges