doc/runtime.tex: Suggest asserting that a stack-allocated object tore down.

doc/runtime.tex: Suggest asserting that a stack-allocated object tore down.

As discussed, it's not an error in itself if an object refuses teardown:
that just means that you can forget about it and it's someone else's
problem now.  But if you really have to deallocate it right now, that's
not going to work.

It might be an idea to introduce a macro to say, essentially,

	{ int rc = sod_teardown(OBJ); assert(!rc); }