- change mesh_get_derived_render to mesh_create_derived_render (always

builds new DerivedMesh... caching can come later)
 - split DerivedMesh returning functions into editmesh and mesh groups
 - got rid of DL_NORS displist type (get built on fly for mesh when
   needed)
 - got rid of Mesh.disp (yay!)
 - started to punch DerivedMesh returning functions into shape to introduce
   modifier stack

source/blender/blenloader/intern/readfile.c

@@ -2086,7 +2086,6 @@ static void direct_link_mesh(FileData *fd, Mesh *mesh)
 	mesh->dvert= newdataadr(fd, mesh->dvert);
 	direct_link_dverts(fd, mesh->totvert, mesh->dvert);
 
-	mesh->disp.first= mesh->disp.last= NULL;
 	mesh->bb= NULL;
 	mesh->oc= 0;
 	mesh->dface= NULL;