Port stats not working correctly: some macOS stats vanished, Linux installs are classified as macOS installs

[barracuda156]

Take a look at bmake stats.

Firstly, there is no stats for > 10.13, even though I have certainly installed it on my powerpc machines, which send stats, and I think on 10.8 as well. That is gone from the site now.

Secondly, a Linux install is classified until macOS versions (with no version). Perhaps make Other OS category for FreeBSD and Linux?

[barracuda156]

And this port shows zero installs despite that I have obviously installed it prior to making a PR: https://ports.macports.org/port/fbzmq/stats