only one saved GP per GP-ident

Conflicts:
	src/graphics/glwrap.cpp
fix ordering of the karts and maybe some more
Save GP reverse Type; close #1137
Save GP on abort
Remove saved GP when we start new race.

Avoid a crash. Saved GP was deleted, but was not NULL. And in other place we have if(m_saved_gp != NULL) check, which was true for deleted object.
Redrawing GP info screen is not needed now.