Bug#422712: gs-esp: pstoraster fails with signal 11 when printing cups testpage

[Troy Rollo <linux@troy.rollo.name>]

On Sunday 23 January 2011, Jonathan Nieder wrote:

> That helps.  If I understand correctly then
>
> 	by = lasty % btile->size.y;
> 	if (by < 0)
> 		by += btile->size.y;
>
> would be another way to convey the same thing.

Probably. The behaviour of the mod operator with negative numbers has been 
undefined at some points in time, and is something that a compiler might get 
wrong - I prefer to avoid applying the modulo function to a negative number 
at all, hence the longer version in my patch.