Updates to z65

[venomix666]

After actually playing a few games I made some updates:

• A couple of missing opcodes have been added
• The status bar was added as it is important in some games (it can be removed by build flags)
• The number of cached paged was increased to improve performance (makes a big difference on systems with slow disk access)
• File saving compression can store maximum 0xFF on unchanged run length instead of 0x80

I have played through Moonglow (it's not very long...) on the Atari 800, the Oric and the BBC Micro and it is completely playable with the increased number of cached pages. Before it was a bit too sluggish at times.

[davidgiven]

Merging. Thanks!