typo and reformatting of comments

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13752 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
allow reinstalling without removing first

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13753 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02