INT 2F PU - Borland TDX - INSTALLATION CHECK                                    
	AX = FB43h
	BX = 0100h
Return: BX = FB43h if loaded
Program: TDX is Borland's Turbo Debugger variant for DPMIsee DOS Protected-Mode Interface programs
Note:	Borland Pascal 7 DPMIsee DOS Protected-Mode Interface programs use this call to check whether they
	  should install their own stack and general protection exception
	  handlers, or allow TDX to handle those exceptions