Fix regression in outputFileExtension
We have to use a QMap (or some other container) which keeps the order (sorted by extension) of the entries because the order incidentally puts "gpg" before "pgp", so that "gpg" is preferred over "pgp" when iterating over the entries looking for an entry matching the classification.
Fixes-commit: 2ba6334d GnuPG-bug-id: 6726