- Replace PYBIND11_PLUGIN with PYBIND11_MODULE
- Fix warnings about symbol visibility by replacing
'namespace pybind11' with 'namespace PYBIND11_NAMESPACE'
- Pybind sets the default visibility of its namespace to 'hidden'
Thus, our export functions like ExportCSG(py::module &m) also are
hidden by default. To work around that define DLL_HEADER
'__attribute__ ((visibility ("default")))
on GNUC platforms.
