Revert "block: Remove deprecated -drive option serial"

This reverts commit b0083267444a5e0f28391f6c2831a539f878d424.

Hold off removing this for one more QEMU release (current libvirt
release still uses it.)

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
14 files changed