Correctly return the result of trivial_copy_n in host/dispatch/copy
Correctly return the result of trivial_copy_n in host/dispatch/copy

Reported by Janick Martinez Esturo

Fixes issue 185

malenie/thrust,allendaicool/thrust,Vishwa07/thrust,Vishwa07/thrust,allendaicool/thrust,levendlee/thrust,bfurtaw/thrust,malenie/thrust,bfurtaw/thrust,google-code-export/thrust,hemmingway/thrust,rdmenezes/thrust,levendlee/thrust,hemmingway/thrust,google-code-export/thrust,Vishwa07/thrust,allendaicool/thrust,google-code-export/thrust,julianromera/thrust,allendaicool/thrust,h1arshad/thrust,julianromera/thrust,malenie/thrust,rdmenezes/thrust,rdmenezes/thrust,hemmingway/thrust,UIKit0/thrust,lishi0927/thrust,h1arshad/thrust,h1arshad/thrust,bfurtaw/thrust,UIKit0/thrust,hemmingway/thrust,Vishwa07/thrust,levendlee/thrust,bfurtaw/thrust,lishi0927/thrust,lishi0927/thrust,lishi0927/thrust,levendlee/thrust,google-code-export/thrust,julianromera/thrust,UIKit0/thrust,UIKit0/thrust,julianromera/thrust,rdmenezes/thrust,malenie/thrust,h1arshad/thrust