Uncomment flattening.
Uncomment flattening.

It will still fail with a runtime-error if you try to use it, but at
least it will compile.  I will need Rasmus's help to finish it.

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