mlprof bug

[Stephen Weeks]

> Well, I only discovered this bug because I wanted to do profiling of a
> self-compile.  Coloring a over a thousand .dot files isn't going to be
> quick in any case, but the faster the better.  And some of those files
> are decent sized.  (As a side note, -keep ssa -keep dot -keep-pass backend
> -keep g on a self compile yields close to 200Meg of data!)

I checked in a solution that overwrites the file in place.  It didn't
affect the speed at all.  See the logs.