Changed checkers field color because pieces were close to invisibel on OS X. I hope this has no negative effect on very dark desktops... .

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@8168 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

test/checkers.cxx

@@ -1170,6 +1170,7 @@ void quit_cb(Fl_Widget*, void*) {exit(0);}
 int FLTKmain(int argc, char** argv) {
   Fl::visual(FL_DOUBLE|FL_INDEX);
   Board b(BOARDSIZE,BOARDSIZE);
+  b.color(FL_BACKGROUND_COLOR);
   b.callback(quit_cb);
   b.show(argc,argv);
   return Fl::run();