[PATCH]Add gnat demangler

[Richard Kenner]

    The following code is taken from H.J. Lu's version of binutils. It
    implements a demangler for the GNAT Ada compiler. The author of this
    code is unknown. I've asked Doug Rupp of GNAT if he knew who wrote the
    code and he said it looked familar, but did not know. Can this code be
    added without knowing the author?

This was written by Arnaud Chalet and Paul Hilfinger, both of whom did
it in their capacity as employees or consultants to ACT and who have
copyright disclaimers on file.

So there is no copyright issue with this.