High score table and other fixes

The game has a high score table including entering a player's name, if the game is running on Spectrum 128K (and compatibles) or Didaktik Gama.

The monkey "dance" music at the end of the game has a better volume envelope.

A graphical error in the introduction (after certain GAME OVERs) is fixed.

An error that did not affect Spectrum because it was only writing to ROM, but caused errors on SAM Coupé, is fixed.