libproj 8.1.0-1

• Rewrite the configure script using autoconf and test it on
  all the platforms supported by rhub.
• Update the internal PROJ copy to 8.1.0.
• Rewrite tests to make sure the C API can be linked to
  and don't skip them on any platform.
• Test using a wrapper package that uses most of the
  exported functions
  (see https://github.com/paleolimbot/rlibproj)
• Update the README with examples of how to make use of this
  package (optionally using Rcpp or cpp11 as a helper)
• Correctly declare system requirements.
• Update configuration options to be more robust across
  environments.

Version 7.1.0-2

v7.1.0-2

proper zstd package on focal

Version 7.1.0-1

v7.1.0-1

try to fix warning for flexible array member