--memory-only option is introduced without compression supported. Now qemu
has support for dumping domain's memory in kdump-compressed format. This
patch adds a new virDomainCoreDumpWithFormat API, so that the format in
which qemu dumps domain's memory can be specified.
Signed-off-by: NQiao Nuohan <qiaonuohan@cn.fujitsu.com>
Signed-off-by: NEric Blake <eblake@redhat.com>