CTL git is missing function exports

[ggarra13]

For building a proper DLL on windows, it is necesary to export all classes and public functions. That needs an .h file with exports like:

if defined(OPENEXR_DLL)

#if defined(ILMCTL_EXPORTS)
        #define ILMCTL_EXPORT __declspec(dllexport)
    #define ILMCTL_EXPORT_CONST extern __declspec(dllexport)
#else
        #define ILMCTL_EXPORT __declspec(dllimport)
        #define ILMCTL_EXPORT_CONST extern __declspec(dllimport)
#endif

else

#define ILMCTL_EXPORT
#define ILMCTL_EXPORT_CONST extern const

endif

and then the classes defined like:

class ILMCTL_EXPORT RcObject { ... };