Remove virtual bool Fl_Graphics_Driver::high_resolution() unlikely to be useful across platforms.

HighDPI support is done with very different means across platforms, so a boolean
value is unlikely to be meaningful across platforms.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3-porting@11950 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

FL/Fl_Graphics_Driver.H

@@ -122,8 +122,6 @@ protected:
   inline int vertex_kind() {return what;}
 #endif
   matrix *fl_matrix; /**< Points to the current coordinate transformation matrix */
-  /** Returns whether the graphics driver is currently drawing to a high resolution surface */
-  virtual bool high_resolution() { return false; }
   virtual void global_gc();
   /** Support function for Fl_Pixmap drawing */
   virtual fl_uintptr_t cache(Fl_Pixmap *img, int w, int h, const char *const*array) { return 0; }