Add generic device implementation of copy.
Add generic device implementation of copy.

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