Fix bad size evaluation
Fix bad size evaluation

xmax, xmin and step are accreal. Therefore, computations are carried out
in both int and double logic. The separate division does introduce a bug
when int logic is used.

Moodstocks/torch7,szagoruyko/torch7,Moodstocks/torch7,diz-vara/torch7,colesbury/torch7,diz-vara/torch7,adamlerer/torch7,szagoruyko/torch7,adamlerer/torch7,colesbury/torch7