Issue an internal warning on first deprecated function call

[Andrew Cagney]

FYI,

The intent was for only one internal-warning message to appear per debug 
session.  Given that an internal-warning message is pretty 
``on-the-nose'' I don't think I could get away with any more than one.

I wrote:

> > The problem behind this was discussed in:
> > http://sources.redhat.com/ml/gdb/2001-03/msg00227.html

(recommended read)

> > The idea is to issue an internal-warning on the first call to a 
> > deprecated [multi-arch] function.

For architecture methods, it's pretty easy -- hook the 
``set_gdbarch_deprecated...()'' calls.  For things like 
write_register_bytes() it is less so.

enjoy,
Andrew