Java, XQuartz and the CLT separate header package aren't required for
everyone's Homebrew usage or a default macOS development install.
As a result, only show then in `brew config` when they are actually
installed.
Use 124 max line length everywhere. Also, reduce tap max line length to
189 as Homebrew/homebrew-core has that as a maximum now. In future
Homebrew/homebrew-core will also be reduced to 124 maximum line length.
Not quite a mass replacement as I've used OS X and Mac OS X where
describing specific older versions and added compatibility methods
for things in the DSL.
