Add some basic infrastructure to generate auxiliary debugging information
for IO registers which can then be used by debuggers.

The perl script is courtesy Knut Schwichtenberg, who also beta-tested the
generated DWARF-2 information.  Many thanks to him!

(Obviously, this still has to be integrated into the build system.)


git-svn-id: http://svn.savannah.nongnu.org/svn/avr-libc/trunk@2361 1084037a-409f-4a99-8160-1a4b3577d4c1