Slightly better debugging for memory block merging.
Slightly better debugging for memory block merging.

diku-dk/futhark,ihc/futhark,diku-dk/futhark,HIPERFIT/futhark,diku-dk/futhark,HIPERFIT/futhark,ihc/futhark,ihc/futhark,HIPERFIT/futhark,diku-dk/futhark,diku-dk/futhark