* ./src/audio_output/aout_s16.c: fixed a segfault. It may have unexpected
    side effects because I don't know this part of the code, but at least
    it doesn't crash anymore.
  * ./plugins/beos/beos.cpp: first attempt at porting the BeOS plugin to the
    new video output and module systems. Doesn't work nor even compile yet.
  * ./configure.in: we now check the gtk-config version.