lib: Add win-dmp crashdump format

lib: Add win-dmp crashdump format

QEMU gained support for 'win-dmp' format in it's release of 3.0,
but libvirt doesn't implement it yet. Fortunately, there not much
needed: new value to virDomainCoreDumpFormat public enum, which
unfortunately means that QEMU driver has to be updated in the
same commit, because of VIR_ENUM_IMPL().

Luckily, we don't need any extra QEMU capability - the code
already checks supported formats via
'query-dump-guest-memory-capability' just before issuing
'dump-guest-memory'.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>