Add improved support for running under the ARAnyM emulator
(Atari Running on Any Machine - http://aranym.org/).

[michael, geert: Cleanups and updates]
Signed-off-by: NPetr Stehlik <pstehlik@sophics.cz>
Signed-off-by: NMichael Schmitz <schmitz@debian.org>
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>