* src/ATC/atis.cxx

* src/ATC/atis.cxx
* src/ATC/atislist.cxx

Patch from Melchior Franz:

- merged the _MWERKS_ & generic #ifdef branch, only the loop head needs
  different treatment
- commented out a "n >> skipeol" that is used in navlist.cxx to gobble
  the starting C++-style comment from default.nav.gz; atis inherited
  that, but there is no such comment in default.atis.gz, so the first
  data entry got thrown away
- commented out min/max frequency exploration (-> only for debugging)
- enhanced the constructor; the operator>> wouldn't have initialized all
  variables in case of a broken default.atis.gz entry, so we would have
  got a mixture of the broken one and the previous one;
- move the automatic FGATIS variable into the loop, so that it gets
  cleanly constructed for every database entry.
- don't access a.type before it is initialized
- updated the commented out debug output statements; they were still
  designed for the FGNav class ...