include: Define constants for parallel save/restore

include: Define constants for parallel save/restore

Add a new VIR_DOMAIN_SAVE_PARALLEL flag to the save and restore APIs,
which can be used to specify the use of multiple, parallel channels
for saving and restoring a domain. The number of parallel channels
can be set using the VIR_DOMAIN_SAVE_PARAM_PARALLEL_CHANNELS
typed parameter.

Signed-off-by: Claudio Fontana <cfontana@suse.de>
Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>