bugfix: crash in "music" fixed

flash_offset was used uninitialized, leading to memory corruption
segment cleanup in snd_play.s
added macro for pascal-style string, for later use

- use pascal style string to have maximum room in font when including
  reverse characters in upper half
add initial console.s

- console driver should handle amigados window content
- first version has support for scrolling one row upwards, included
  testcode in amigados.s