We've dumped all the snapshot helpers and related code into
qemu_driver.c. It accounted for ~10% of overal size of qemu_driver.c.
Separate the code to qemu_snapshot.c/h.
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
