Get rid of underscore.c

[Nick Clifton]

Hi Zack,

> > This has just broken binutils builds.  Binutils currently builds its own 
> > copy of cxxfilt and now it has no main function.
> 
> My recommendation is to drop cxxfilt from binutils.  Patch appended.

Err that seems a little bit draconian to me.  Why shouldn't the
binutils package provide a C++ demangler.  (Answer: because G++ now
does so).  But why should G++ have its own demangler ?  Why not use
the binutils one ?  (Possible answer: because the G++ guys want to
control the demangler ?)

Personally I would prefer to keep cxxfilt in binutils and just copy
the current gcc/cp/cxxfilt.c file there.  It might get out of sync
with gcc, but there are plenty of other files that we try to keep in
sync between the two projects, so adding one more will not hurt.  We
can even add prominent notices to both source files saying "if you
change this file, change its cousin too".

Cheers
        Nick