Revert back OGLGraphics class to fix Android and Raspberry-Pi build.

Source/Engine/Graphics/OpenGL/OGLGraphics.cpp

@@ -234,10 +234,8 @@ Graphics::Graphics(Context* context_) :
     deferredSupport_(false),
     anisotropySupport_(false),
     dxtTextureSupport_(false),
-#ifdef GL_ES_VERSION_2_0
     etcTextureSupport_(false),
     pvrtcTextureSupport_(false),
-#endif
     sRGBSupport_(false),
     sRGBWriteSupport_(false),
     numPrimitives_(0),

Source/Engine/Graphics/OpenGL/OGLGraphics.h

@@ -488,12 +488,10 @@ private:
     bool anisotropySupport_;
     /// DXT format support flag.
     bool dxtTextureSupport_;
-#ifdef GL_ES_VERSION_2_0
     /// ETC1 format support flag.
     bool etcTextureSupport_;
     /// PVRTC formats support flag.
     bool pvrtcTextureSupport_;
-#endif
     /// sRGB conversion on read support flag.
     bool sRGBSupport_;
     /// sRGB conversion on write support flag.