Implement the cpp-only path of fill with cudaMemset when appropriate.
Implement the cpp-only path of fill with cudaMemset when appropriate.

Fixes issue 143

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