Armature "XRay mode" now draws nicely with solid too. For it to work, I

had to add a new feature to the 3d window, to collect "after draw" objects,
which get drawn as last, after a clear of the zbuffer.

Same method can be used for nice OpenGL transparent draw, the system is
ready for it, do that later.

The huge commit is caused by cleaning up globals from struct Global. Many
variables were unused or just not needed anymore. Did that to move the ugly
G.zbuf to where it belongs, in the View3D space struct. :)

source/blender/src/transform_constraints.c

@@ -692,7 +692,7 @@ void BIF_drawConstraint(void)
 				glVertex3fv(vec); 
 			glEnd();
 			setlinestyle(0);
-			if(G.zbuf) glEnable(GL_DEPTH_TEST);	// warning for global!
+			if(G.vd->zbuf) glEnable(GL_DEPTH_TEST);	
 		}
 
 		if (tc->mode & CON_AXIS0) {