Add simplifyUnOp rule.
Add simplifyUnOp rule.

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