* Bump MPLS_MAX_LABELS from 2 to 16;
* Adjust the static_nh_label structure and the mpls_label2str() function;
* On OpenBSD, print an error message when trying to push more than one
label at once (kernel limitation). While here, add support for MPLSv6
FTNs in OpenBSD.
This is not the full package. We still can't pop multiple labels at once,
or do things like swap a label and push other ones. We'll address that
in the future.