Also hide intra-group parallelism behind a flag for now.
Also hide intra-group parallelism behind a flag for now.

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