added missing #include to discrete_voronoi example
added missing #include to discrete_voronoi example

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