Introduce a virDomainOpenConsole API

Introduce a virDomainOpenConsole API

To enable virsh console (or equivalent) to be used remotely
it is necessary to provide remote access to the /dev/pts/XXX
pseudo-TTY associated with the console/serial/parallel device
in the guest. The virStream API provide a bi-directional I/O
stream capability that can be used for this purpose. This
patch thus introduces a virDomainOpenConsole API that uses
the stream APIs.

* src/libvirt.c, src/libvirt_public.syms,
  include/libvirt/libvirt.h.in, src/driver.h: Define the
  new virDomainOpenConsole API
* src/esx/esx_driver.c, src/lxc/lxc_driver.c,
  src/opennebula/one_driver.c, src/openvz/openvz_driver.c,
  src/phyp/phyp_driver.c, src/qemu/qemu_driver.c,
  src/remote/remote_driver.c, src/test/test_driver.c,
  src/uml/uml_driver.c, src/vbox/vbox_tmpl.c,
  src/xen/xen_driver.c, src/xenapi/xenapi_driver.c: Stub
  API entry point