Building the GUI on windows

[crobi]

I get lots of compiler errors in vertexdatainterpreter.cpp (resulting from WINGDIAPI and APIENTRY being undefined inside gl.h).

The file includes GL/gl.h without including windows.h, which seems to be necessary.

In GLee.h (an extension loading library), the include block looks as follows:

#ifdef WIN32
    #ifndef WIN32_LEAN_AND_MEAN
    #define WIN32_LEAN_AND_MEAN
    #endif
    #include <windows.h>
    #include <GL/gl.h>
#elif defined(__APPLE__) || defined(__APPLE_CC__)
    #define GL_GLEXT_LEGACY
    #include <OpenGL/gl.h>
#else // GLX
    #define __glext_h_  /* prevent glext.h from being included  */
    #define __glxext_h_ /* prevent glxext.h from being included */
    #define GLX_GLXEXT_PROTOTYPES
    #include <GL/gl.h>
    #include <GL/glx.h>
#endif

In glext.h, there is the following block:

#if defined(_WIN32) && !defined(APIENTRY) && !defined(__CYGWIN__) && !defined(__SCITECH_SNAP__)
#define WIN32_LEAN_AND_MEAN 1
#include <windows.h>
#endif

[jrfonseca]

It should be fixed with my latest change. Thanks.