INT E0 - REAL/32 - "DEV_SETFLAG" - SET SYSTEM FLAG

	CL = 85h
	DX = system flag ID
Return: AX = status (0000h success, else error code)
Note:	REAL/32 returns an error if the flag was already set, which indicates
	  that a previous logical interrupt has not yet been serviced
SeeAlso: INT E0/CL=84h