PATCH: fix PR 22232

[Paolo Bonzini]

Ben Elliston wrote:
> I've Cc'ed Per as he has hacked on this script and I can't work out who
> else might be its maintainer.
> 
> This patch fixes a problem reported in PR 22232.  Although the bug
> submitter has long since worked around the problem, his complaint has
> identified an obvious bug in fixprotos.  The submitter reported that the
> script misbehaved when he had a source (or build?) subdirectory
> consisting of a single letter (d/), such that it was matched by the
> regular expression "^./"
> 
> If we really want to match ./ as typically produced by find(1), we
> should escape it properly.  Okay for stage 1?

Okay now unless someone objects in 48 hours.

Paolo