Enforce a port to depend on a version less than one given

[José G. Juanino]

Hi FreeBSD ports,

I am the maintainer of archivers/py-borgbackup, and the 1.1.5 release 
has a unusual dependency: it depends on msgpack-python >= 0.4.6 but < 
0.5.0. What is the proper way to accomplish this in the Makefile port?  
There is a bug report (227717) about that, as consequence of upgrading 
devel/py-msgpack to 0.5.6. Regards.


-- 
José G. Juanino