progs/demos: fix glut initialization calls

Remove glutInitWindowPosition() calls to play nicer with window managers.

Move glutInitWindowSize() calls before glutInit() so the the default window
size can be overridden by the -geometry cmd line option.

progs/demos/gamma.c

@@ -146,12 +146,9 @@ display(void)
 int
 main(int argc, char **argv)
 {
+  glutInitWindowSize(500, 400);
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
-
-  glutInitWindowPosition(50, 50);
-  glutInitWindowSize(500, 400);
-
   glutCreateWindow("gamma test patterns");
   glutReshapeFunc(Reshape);
   glutDisplayFunc(display);