Make cloog-ppl015 keg_only.
Make cloog-ppl015 keg_only.

* Conflicts with cloog in main repository.

UniqMartin/homebrew-versions,Ashton-W/homebrew-versions,heuermh/homebrew-versions,jimhe/homebrew-versions,DomT4/homebrew-versions,coeligena/homebrew-verscustomized