Log Message:
Changes 0.5.0:
* Memory management change: memory allocation functions now abort on failure.
  Leads to simpler code both internally and for users of the library.
* Support for tape acceleration.
* IDE improvements to allow DivIDE to support FATware.
* New API to deal with flagging automatic snapshots in RZX files.
* New function to get length (time) of a tape block.
* 128K SNA files are now treated as being for the Pentagon 128 rather than
  the Spectrum 128.
* SNA files now written out correctly.
* Handle MDR write protection flag correctly.
* Allow MDR images with bad checksums to load (the error will be handled by
  the If1 ROM).
* Support saving custom ROMs in SZX snapshots.
* Support for DivIDE, Kempston mouse and the simple IDE interface
  in SZX snapshots.
* Allow building without libgcrypt.
* Amiga and MorphOS compilation fixes.
* Don't produce empty libraries to fix build process on OpenSolaris.
* Remove deprecated functions.
* Tweak timings for TS2068.