INT 16 U - PCIBM PC Tools v5.1-8.0 DESKTOP - CHECK WHETHER DESKTOP LOADED RESIDENT
	AX = FFC5h
Return: BL = Desktop state
	    00h if nonresident
	    nonzero if loaded resident
Note:	available only when popped up; should call AX=FFEFh first to ensure
	  that DESKTOP is active
SeeAlso: AX=FFEFh,AX=FFF3h