Policy on upgrading dependents

[Ryan Schmidt]

If I maintain a library (libpng for example) and I update it to a new version that has a new library version, which requires all dependents of that library to be rebuilt, then it should be my responsibility to also commit the revbump on all the ports that use that library. Does anyone disagree? This would be an exception from our usual policy of requiring the consent of the maintainers of other ports, but in this case, upgrading the library without rebuilding those other ports would cause those other ports to break, so I feel it's the library maintainer's responsibility to ensure the least breakage.

This thought was prompted by tickets like:

https://trac.macports.org/ticket/29460