INT E0 - REAL/32 - "DEV_WAITFLAG" - WAIT ON SYSTEM FLAG

	CL = 84h
	DX = system flag ID
Return: AX = status (0000h success, else error code)
	if successful, this function does not return until the system flag has
	  been set by an interrupt handler (see INT E0/CL=85h); if the flag was
	  already set, this call returns immediately
SeeAlso: INT E0/CL=85h,INT E0/CL=B7h