INT 2D - DTown Utilities v1.40+ - GET POP-UP HANDLER ADDRESS

	AL = 20h
Return: AL = FFh if available
	    DX:DI -> DTU popup-handler
Program: DTown Utilities is a freeware programmer's utility TSR by Jeroen van
	  Disseldorp
Note:	this function is only available if the extended API has been installed
	  in the resident portion
SeeAlso: INT 2D/AL=10h"DTown",INT 2D/AL=21h,INT 2D/AL=50h,INT 2D/AL=51h
SeeAlso: INT 03"DTown"