It seems that all the library projects have their own copies of this,
which seems kinda silly.  And there are some downsides to those files:

* The visibility alias file generation script is written in perl.  This
  isn't generally a bad thing, but requires people have perl installed.
  With the meson build, python will be required, so might as well write
  it in python.
* The symbols file consumed by the scripts is a C preprocessor file, and
  its a bit tedious, annoying, and error-prone to write.  The new format
  that the new scripts consume is simple and easy to read and write.

There was also never really any documentation for how to set all this
up, so I've written a README that describes the process for both
autotools and meson.