Patch from Melchior Franz:

Patch from Melchior Franz:

- merged the _MWERKS_ and the generic branch, only the loop head needs
  different treatment
- created a constructor; the operator>> wouldn't have initialized all
  variables in case of a broken default.fix.gz entry, so we would have
  got a mixture of the broken one and the previous one; (valgrind
  complained ...)
- move the automatic FGFix variable into the loop, so that the gets
  cleanly constructed for every database entry.
- don't access fix.type before it is initialized
- updated the commented out debug output statements (they were copied
  over from navlist.cxx but never adapted)