OpenSystemsDevelopment / qpdf

gcc already warns for undefined variables, but this is in preparation
for Google's oss-fuzz, which builds in this way.

See https://github.com/Alexpux/MINGW-packages/issues/4543

The Azure pipeline does all the artifact creation now.

Since the files autogen.sh creates are now controlled, you only have
to run autogen.sh when you modify the source files, not when you
build from a clean checkout.

to avoid line ending problems

Update documentation to reflect that automatically generated files are
committed. Detect when they are outdated if we have the ability to
regenerate them.

libtool make install already works this way.

Use free Azure Pipelines to do Linux, Windows, and Mac build and test
and to generate Windows binary distributions.

This creates a zip file of the files that are present in a source
distribution but not present in the repository.