Fix MacOS compilation on C++11 and C++14 (boostorg#93)

Fixes boostorg#92

Switch to std::shared_ptr from boost::shared_ptr and provide a BOOST_… (

boostorg#90)

…DLL_USE_BOOST_SHARED_PTR compatibility macro to restore the old behavior

Fixes boostorg#75

Add support for modular build structure. (boostorg#71)

This is part of the effort to make the Boost libraries "modular" for build and consumption. See https://lists.boost.org/Archives/boost/2024/01/255704.php and https://github.com/grafikrobot/boost-b2-modular/blob/b2-modular/README.adoc for more information.

This PR depends on the following other PRs being merged to both develop and master branches of the respective repos:

- boostorg/boost#854

Add support for modular build structure. (boostorg#71)

This is part of the effort to make the Boost libraries "modular" for build and consumption. See https://lists.boost.org/Archives/boost/2024/01/255704.php and https://github.com/grafikrobot/boost-b2-modular/blob/b2-modular/README.adoc for more information.

This PR depends on the following other PRs being merged to both develop and master branches of the respective repos:

- boostorg/boost#854

Update copyright years

Update copyright years

Update copyright years

Update copyright years

CI fix attempt (1)

CI fix attempt (1)