INT 2F U - DOS 3.0+ internal - OPEN DEVICE AND SET SFTsee System File Table OWNER/MODE
	AX = 120Ch
	SDAsee Swappable Data Area current SFTsee System File Table pointer -> SFTsee System File Table for file
	DS = DOS DS
	SS = DOS DS (must be using a DOS internal stack)
Return: ES, DI, AX destroyed
Notes:	invokes "device open" call on device driver for SFTsee System File Table
	changes owner of last-accessed SFTsee System File Table to calling process if it was opened
	  via FCBsee File Control Block
	called by network redirectors such as MSCDEX