Just an update from my side. I kinda got it working by copy/pasting some stuff from the private headers. Not a really nice solution as it means I will have to keep everything I copied up to date. But the good news is that I now have quad buffer stereo working under windows.
I have seen more people asking about how to get the opengl functions working on the forums. So here is how I did for future reference. The trick is to redefine the opengl functions again (see the DECLARE_GL_ENTRYPOINTS and ENUM_GL_ENTRYPOINTS_ALL declarations in OpenGLWindows.h). I also had a weird problem that when building the ‘development editor’ configuration I got unresolved symbols for the functions but when building the ‘development (game)’ configuration it could resolve them. Because of this I had to make use of the defines the build system sets to distinguish between the two configurations and for the editor I had to extract the extract points all over again.
For the opengl device context I had to include “OpenGLResources.h” and copy/paste FPlatformOpenGLContext struct definition from the private headers.