compare rust type with llvm value in result, lval_result

Right now in trans we have this result and lval_result that is the combination of a bcx and a value. It should also include the rust type of this value. This would make it possible to figure out, based solely on result and lval_result, whether something is stored on the stack or not. Right now we have to check if the kind is owned and if the type is immediate.

Seems like this is obsolete since trans uses datum now? Closing.