Log Message:
Changes 0.2.1:
* Transparent reading of bzipped and gzipped files.

* Add support for writing emulator custom data to .rzx and .szx files.

* Update to the more recent version of gcrypt; version 1.1.42 or
  later is now required.

* Link libspectrum against gcrypt, glib and zlib; this means that
  client applications no longer need to do this.

* Support for 'the last instruction was an EI' in the snapshot code.

* Routines to check the versions of libspectrum and gcrypt in use.

* Write .rzx files with a version number of 0.12 if we're not
  signing the data; improves backward compatability.

* Fix a segfault when dealing with .slt files.

* QNX6 compilation fixes.