Doc typo.

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14603 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
[whitespace] bring threads/pervasives.ml closer to stdlib/pervasives.ml

(report by Hugo Heuzard)

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14604 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02