Please add VRPN to MacOS builds

[apenngrace]

@rdb, a few minutes ago I chatted with you on IRC regarding VRPN support (pasted below), and you let me know that it should be supported but support seems to have been taken out of MacOS builds. I would greatly appreciate that fix! Thanks so much!

[18:00] <andrew_> Does panda3d still support vrpn?
[18:00] <rdb> Yes
[18:01] <rdb> I don't know how well it still works because I don't know if anyone is using it
[18:01] <rdb> But we do still build with VRPN support
[18:01] <andrew_> Ok, where do I find it in the API?  I'm getting an error with `panda3d.vrpn import *` for example
[18:02] <andrew_> I get `ImportError: No module named vrpn`
[18:02] <rdb> Where did you install panda3d from?
[18:02] <andrew_> pip
[18:02] <rdb> Which OS?
[18:02] <andrew_> macos
[18:02] <rdb> And Python version?
[18:02] <andrew_> 3.7
[18:02] <rdb> Evidently we don't build the mac builds with VRPN, apologies about that
[18:03] <rdb> I'll have to look into that
[18:03] <rdb> Another day though, i really have to leave right now
[18:03] <andrew_> thanks

[Moguri]

@rdb Is this something we want to solve for 1.10? Is there something (e.g., is VRPN a pain to build on macOS) that would make this difficult?

[rdb]

Actually I just got done rebuilding the thirdparty packages for macOS on the buildbot, which now include VRPN, so @apenngrace please give the next builds a go when they become available on the download page in some number of hours.

[rdb]

Closing this since I can import and instantiate a VrpnClient with the latest development wheel.