[Bro-Dev] Generate bro documentation

[Jonathan Siwek]

> So question is: should cmake try to figure out if there's an awkwardly named sphinx-build binary so it works with MacPorts? Or is there a way that I can tell MacPorts to create a symlink for the binary.

I don't know about getting MacPorts to do that, but the CMake script could be made more configurable about finding the right "sphinx-build" -- the typical Find* package macros could be used instead of hardcoding it like it is now.

- Jon