Adding cgal-cpp to pinnings

[jakirkham]

Would like to suggest adding cgal-cpp. Here's the ABI Laboratory review ( though it needs to be refreshed lvc/abi-tracker#18 ). It's used in a handful of packages where it is either unpinned or pinned manually in the recipe. Also as it depends on boost-cpp there some value in basing migrations of cgal-cpp on boost-cpp.

cc @conda-forge/cgal-cpp @conda-forge/cgal