Initial CRAN-oriented release: vendored CppAD 20260000.0 headers
with ColPack/Eigen/ADOLC/IPOPT disabled in configure.hpp,
R-safe ErrorHandler (REprintf /
Rf_error), and std::cout redirects to a
discard stream for CRAN compiled-code checks.
Inline CppAD::local::temp_file() so LinkingTo packages
do not need libcppad_lib (headers-only packaging).