fix build '--with-sound=no'
rdevice.c: remove warning about no prototype for snprintf() on Linux
rdevice.c: default TTY_DEV_NAME is also also valid for NetBSD/amd64 and FreeBSD/amd64
atari_x11.c: don't auto-repeat the 'screenshot' key
debian/README.Debian: fix a typo
Some fixes for "basic" target
add write support for Olivetti M20 floppy images
toplevel makefile: fix 'cleansrc' target for Unix/Linux