Beta 5:

Biggest A500 cycle-exact updates should be done now.

* interrupt delay rewritten and corrected, fixes Gleat Stuff #01/BRB
* blitter/CPU timing tweak, fixes 1010 bobs/Celtic
* disable sound if sound driver buffer position gets stuck (driver bug)
* final partition read/write fix
* try to emulate reading of non-existing/write-only custom registers more accurately
* Brian the Lion "dialog screen" seems to be something AGA specific after all... 1 extra cycle needed after write to BPLCON0 before BPL cycle diagram changes (or at least in Brian the Lion´s situation) so add one cycle in AGA and hope it isn´t totally incorrect fix