"Dope" demo bugs (DOSBox-X's fault)

BUG: Noticeable pause of music at points where VGA BIOS is called to set video mode during demo

     However, this pause also happens on real hardware if the BIOS does not use the IRQ for hard
     disk access (tested on a Pentium MMX 133MHz with a CompactFlash card for a hard disk).

BUG: You can only run the demo once. Additional attempts log "illegal instruction" messages and
     crash back to the DOS prompt. You must close and reopen DOSBox-X to run the demo again.

 - I know for a fact that is not a feature of the demo. Having run it on real hardware, I know
   the demo can be run again after the first time (though it is not reliable at reinitializing
   the GUS to a known state).

 - The debug messages from DOSBox-X are:

   Warning: Illegal read from b66b1da, CS:IP 8: b66700a
   DYNX86:Can't run code in this page!
   Warning: Illegal read from b66b1da, CS:IP 8: b66700a
   Warning: Illegal read from b66b1db, CS:IP 8: b66700a
   141992554: CPU:CPU:66:GRP5:Illegal call  7
   Warning: Illegal read from b66b1da, CS:IP 8: b66700a
   Warning: Illegal read from b66b1da, CS:IP 8: b66700a
   Warning: Illegal read from b66b1db, CS:IP 8: b66700a

 - This apparently only happens if "private area size" is less than 16384, regardless of
   "mainline compatible mapping" and "private area in umb" settings. Hm... is DOSBox
   writing things beyond the block of private space it just allocated?

