handling of generated info pages

[Roland McGrath]

For the most part we only put generated files in the repo when they
are things that are necessary to do the build.  The bar for putting
more generated files into the repo should be quite high.  I think
we're also pretty happy overall with the distribution-generation
scheme wherein just 'git archive' is enough, so generating files for
tarballs that are not in the repo would be a regression there and
more headaches for release managers.

Building (including building the documentation) failing with newer
tools is just a bug like any other.  For past releases it is just a
question of how much backporting the release manager for that
particular branch wants to deal with.