[PATCH]Add gnat demangler

[Ken Block]

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 patch assumes that the JAVA patch has already been applied.