RiscOS 3.1 patch

To install the patch, first unpack the main zip file and install the
main program by dragging it into the directory in the usual RiscOS way.

Unpack the patch zip file in a similar way, then drag the patch !DragonAdv
over the top of the main !DragonAdv application.

The patch is just the main !DragonAdv runfile with the 'RiscPC present' 
variable near the start changed to zero, and Rick Hudson's old PlaySample 
module which, if present, will be used instead of the Playit module.