The old syntax was

   -chardev SOMECONFIG
   -nic user,guestfwd=tcp:IP:PORT-chardev:CHARDEV

The new syntax is

   -chardev SOMECONFIG
   -netdev user,guestfwd=tcp:IP:PORT,chardev=ID,id=user-ID

The current character device syntax uses either

  -serial tty,path=/dev/ttyS2

Or

  -chardev tty,id=serial0,path=/dev/ttyS2 -serial chardev:serial0

With the new -device support, we now prefer

  -chardev file,id=serial0,path=/tmp/serial.log -device isa-serial,chardev=serial0

This patch changes the existing -chardev syntax to use this new
scheme, and fallbacks to the old plain -serial syntax for old
QEMU.

The monitor device changes to

  -chardev socket,id=monitor,path=/tmp/test-monitor,server,nowait -mon chardev=monitor

In addition, this patch adds --nodefaults, which kills off the
default serial, parallel, vga and nic devices. THis avoids the
need for us to explicitly turn each off

Change -monitor, -serial and -parallel output to use -chardev if it is
available.
* src/qemu/qemu_conf.c: Update qemudBuildCommandLine to use -chardev where
  available.
* tests/qemuxml2argvtest.c tests/qemuxml2argvdata/: Add -chardev equivalents
  for all current serial and parallel tests.

We keep support for the pty based monitor so that we can re-connect
to VMs started by older versions of libvirtd.

* src/domain_conf.c: handle formatting and parsing unix monitors

* src/qemu_driver.c: add qemudOpenMonitorUnix(), remove the monitor
  pty path searching from qemudFindCharDevicePTYs(), switch
  qemudStartVMDaemon() and qemuDomainXMLToNative() to using a unix
  monitor

* tests/qemuxml2argvtest.c: switch to using a unix monitor

* tests/qemuxml2argvdata/qemuxml2argv-*.args: update test data

virExec will write out the pid of the daemonized process only. Use this
in the QEMU driver, rather than QEMU's pidfile, so we can catch errors we
might miss if the emulator bails early.

* tests/qemuxml2argvtest.c (testCompareXMLToArgvFiles): Adjust the
code that creates "actual" output, so that it too produces a
newline-terminated buffer.
* tests/qemuxml2argvdata/*.args: Append a newline to each, via:
for i in $(find|grep '\.args$'); do echo >> $i;done