Add missing import for GHC 7.8.
Add missing import for GHC 7.8.

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