Fix prettyprinting of unsigned modulo.
Fix prettyprinting of unsigned modulo.

HIPERFIT/futhark,ihc/futhark,CulpaBS/wbBach,ihc/futhark,ihc/futhark,mrakgr/futhark,diku-dk/futhark,diku-dk/futhark,mrakgr/futhark,diku-dk/futhark,mrakgr/futhark,diku-dk/futhark,HIPERFIT/futhark,diku-dk/futhark,HIPERFIT/futhark