This patch changes how parameters are passed to dnsmasq.  Instead of
being on the command line, the parameters are put into a file (one
parameter per line) and a commandline --conf-file= specifies the
location of the file.  The file is located in the same directory as
the leases file.

Putting the dnsmasq parameters into a configuration file
allows them to be examined and more easily understood than
examining the command lines displayed by "ps ax".  This is
especially true when a number of networks have been started.

When the use of dnsmasq was originally done, the required command line
was simple, but it has gotten more complicated over time and will
likely become even more complicated in the future.

Note: The test conf files have all been renamed .conf instead of
.argv, and tests/networkxml2xmlargvdata was moved to
tests/networkxml2xmlconfdata.

The DHCPv6 support includes IPV6 dhcp-range and dhcp-host for one
IPv6 subnetwork on one interface.  This support will only work
if dnsmasq version >= 2.64; otherwise an error occurs if
dhcp-range or dhcp-host is specified for an IPv6 address.

Essentially, this change provides the same DHCP support for IPv6
that has been available for IPv4.

With dnsmasq >= 2.64, support for the RA service is also now provided
by dnsmasq (radvd is no longer used/started). (Although at least one
version of dnsmasq prior to 2.64 "supported" IPv6 Router
Advertisement, there were bugs (fixed in 2.64) that rendered it
unusable.)

Documentation and the network schema has been updated
to reflect the new support.

The regression testing done by comparison of command-line
generated from the network XML file and the expected
command-line arguments (read from file).
Signed-off-by: NMichal Novotny <minovotn@redhat.com>

This commit adds support for IPv6 parsing and formatting to the
virtual network XML parser, including moving around data definitions
to allow for multiple <ip> elements on a single network, but only
changes the consumers of this API to accommodate for the changes in
API/structure, not to add any actual IPv6 functionality. That will
come in a later patch - this patch attempts to maintain the same final
functionality in both drivers that use the network XML parser - vbox
and "bridge" (the Linux bridge-based driver used by the qemu
hypervisor driver).

* src/libvirt_private.syms: Add new private API functions.
* src/conf/network_conf.[ch]: Change C data structure and
  parsing/formatting.
* src/network/bridge_driver.c: Update to use new parser/formatter.
* src/vbox/vbox_tmpl.c: update to use new parser/formatter
* docs/schemas/network.rng: changes to the schema -
  * there can now be more than one <ip> element.
  * ip address is now an ip-addr (ipv4 or ipv6) rather than ipv4-addr
  * new optional "prefix" attribute that can be used in place of "netmask"
  * new optional "family" attribute - "ipv4" or "ipv6"
    (will default to ipv4)
  * define data types for the above
* tests/networkxml2xml(in|out)/nat-network.xml: add multiple <ip> elements
  (including IPv6) to a single network definition to verify they are being
  correctly parsed and formatted.