Document point of map4 test.
Document point of map4 test.

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