Fortran API is not exported on Windows

[econwang]

I compile the lib with cmake and msvc, the resulting lib works well when call from a C program, but can not call from a fortran program, seems that it does not export fortran api nlo_*.

[stevengj]

Yes, it looks like you are right — on Windows, you need this __declspec(dllexport) decorator in order to export functions. For the regular C API, we have an NLOPT_EXTERN macro that adds this decorator as needed, but we aren't utilizing this in the Fortran API definitions.