Reformat configure instructions
Reformat configure instructions

MacOS X and Mac OS X changed to OS X.

msprotz/ocaml,gerdstolpmann/ocaml,msprotz/ocaml,eliberis/ocaml,yunxing/ocaml,msprotz/ocaml,eliberis/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,eliberis/ocaml,msprotz/ocaml,eliberis/ocaml,eliberis/ocaml,gerdstolpmann/ocaml,msprotz/ocaml,yunxing/ocaml,gerdstolpmann/ocaml,yunxing/ocaml,yunxing/ocaml,yunxing/ocaml