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/FrameBuffer.h

@@ -25,11 +25,6 @@
 #include <EGL/egl.h>
 #include <stdint.h>
 
-#if defined(__linux__) || defined(_WIN32) || defined(__VC32__) && !defined(__CYGWIN__)
-#else
-#warning "Unsupported Platform"
-#endif
-
 typedef uint32_t HandleType;
 typedef std::map<HandleType, RenderContextPtr> RenderContextMap;
 typedef std::map<HandleType, WindowSurfacePtr> WindowSurfaceMap;