Log Message:
Changes 0.6.2:
* Add some small bits of system information (OS, libspectrum
  version) into creator custom data for formats which support this.

* QNX6 compilation fixes and package file.

* rzxcheck: return 1 if the RZX file does not have a good signature.

* rzxdump: use libgcrypt 1.1.42 or later.

* snap2tzx: new utility to convert snapshots to tape files.
  Heavily based on Tomaz Kac's 'z802tzx'.

* tapeconv: remove double-free bug if tape reading fails.