Add a function for generically dumping the ImageInfoSpecific information
in a human-readable format to block/qapi.c.
Use this function in bdrv_image_info_dump and qemu-io-cmds.c:info_f to
allow qemu-img info resp. qemu-io -c info to print that format specific
information.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>