Fixed RLPs being constructed for deallocated memory

RLP constructor taking a vector reference and working with a pointer to internal vector data can access deallocated memory in case vector is destroyed after the construction.  
This fixes all such cases where the vector passed is rvalue.
Alternative solution would be for RLP to own a moved vector and probably share it with other spawned RLPs
This is a non-issue. See http://stackoverflow.com/questions/584824/guaranteed-lifetime-of-temporary-in-c