Add Falk Hueffner as GNATS only maintainer

[Wolfgang Bangerth]

I have just added Falk Hueffner as an additional GNATS only maintainer.  
Falk has the unique advantage over the rest of us GNATS people that he has
access to a variety of different platforms, through the debian project, in
particular to Alpha. I think this comes in handy given that we have ever
so many reports about non-x86 platforms that nobody has ever looked at. In
addition, he also has some knowledge of gcc proper, so maybe we get to see
more of his fixes in the future!

Welcome in the brotherhood :-)
  W.

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Wolfgang Bangerth              email:            bangerth@ices.utexas.edu
                               www: http://www.ices.utexas.edu/~bangerth/