INT 2F U - TRAP.COM - INSTALLATION CHECK                                        
	AX = DA55h
	DL = interrupt number
	DH = ???
Return: if installed
	    AH = interrupt number
	    AL = ???
	    ES:BX -> ???
Program: TRAP is an interrupt call tracer by Patrick Phillipot/Udo Chrosziel
Note:	a separate copy of TRAP is loaded for each interrupt to be traced; thus
	  the interrupt number is part of the installation check