opengl renderer: Enable and fix renderer Mac support

The following enables the renderer build on darwin.
Moved platform specific type declarations from render_api.h
to render_api_platform_types.h so it can be included from the
objective c code.
Fixed subwindow to use EmuGLView which overrides NSView to prevent
background drawing of the view.

tools/emulator/opengl/host/libs/libOpenglRender/WindowSurface.cpp

@@ -228,7 +228,14 @@ void WindowSurface::copyToColorBuffer()
                           GL_RGBA, GL_UNSIGNED_BYTE, data);
     }
 
+//
+// XXX: for some reason flipping the image is not required on
+//      Mac. Need to find the reason, currently unkbown.
+//
+#ifndef __APPLE__
 #define FLIP_BUFFER 1
+#endif
+
 #if FLIP_BUFFER
     //We need to flip the pixels
     int bpp = 4;