Minor grammar fixes

On Tue, Aug 12, 2014 at 07:11:14AM -0700, Jason Gross wrote:
> In theories/PArith/BinPosDef.v:
> 
> > @@ -18,7 +18,7 @@
> >
> >  Require Export BinNums.
> >
> > -(** Postfix notation for positive numbers, allowing to mimic
> > +(** Postfix notation for positive numbers, which allows mimicing

mimicking?

In any case, thanks for spotting these errors.

Hugo