GSdx-d3d: purge GSDrawingContext* context and GSDrawingEnvironment env from GSRendererDX.h

Not used anywhere in dx code and the code is already defined in
GSState.h with member variable names.

plugins/GSdx/GSRendererDX.h

@@ -48,9 +48,6 @@ protected:
 
 	bool DATE;
 
-	GSDrawingContext* context;
-	GSDrawingEnvironment env;
-
 	GSDeviceDX* dev;
 
 	GSDeviceDX::VSSelector m_vs_sel;