Better separate printer-specific code using virtual Fl_GDI_Printer_Graphics_Driver::draw(Fl_Bitmap*...)

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10110 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Check for use of the Fl_GDI_Printer_Graphics_Driver class to detect printer usage.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10111 ea41ed52-d2ee-0310-a9c1-e6b18d33e121