Define STRICT_R_HEADERS, use M_PI

[eddelbuettel]

Dear Samuel, dear compas team,

Your CRAN package compas uses Rcpp, and is affected if we add a definition of STRICT_R_HEADERS as we would like to do. Please see the discussion at
RcppCore/Rcpp#1158
and the links therein for more context on this.

First off, I hope I have the right repo. On CRAN it is compas with one s, here it is compass with two s -- and the set of files is slightly different. I can email you a suggested patch for the CRAN version if you prefer. But GitHub may be easier.

Here, I prefixed one #include <Rcpp.h> with STRICT_R_HEADERS (it could also be added in all files if you prefer) and made one additional change that is needed by moving from PI to M_PI.

It would be lovely if you could apply this. There is no strong urgency: we aim to get this done over all affected packages in the space of a few months. If you apply it, would you mind dropping me a note by email or swinging by
RcppCore/Rcpp#1158
to confirm?

Many thanks for your help, and I hope you continue to find Rcpp helpful. Please don't hesitate to ask if you have any questions.