Improve futhark-dataset manpage.
Improve futhark-dataset manpage.

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