- open midi/wave output files only when output starts (to avoid empty/useless   files if device is not used) - avoid segfault when midi output init fails
- open midi/wave output files only when output starts (to avoid empty/useless
  files if device is not used)
- avoid segfault when midi output init fails

marmolejo/bochs-zet,marmolejo/bochs-zet,marmolejo/bochs-zet,marmolejo/bochs-zet,marmolejo/bochs-zet