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/NativeSubWindow.h

@@ -17,7 +17,11 @@
 #define NATIVE_SUB_WINDOW_H
 
 #include <EGL/egl.h>
-#include "libOpenglRender/render_api.h"
+#include "libOpenglRender/render_api_platform_types.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
 
 EGLNativeWindowType createSubWindow(FBNativeWindowType p_window,
                                     EGLNativeDisplayType* display_out,
@@ -26,4 +30,8 @@ EGLNativeWindowType createSubWindow(FBNativeWindowType p_window,
 
 void destroySubWindow(EGLNativeDisplayType dis,EGLNativeWindowType win);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif