INT 2F U - IFSFUNC.EXE (DOS 4.x only) - ???
AX = 112Dh
BL = subfunction (value of AL on INT 21)
04h truncate open file to zero length
ES:DI -> SFT for file
Return: CF clear
else ???
Return: CX = ??? (00h or 02h for DOS 4.01)
ES:DI -> SFT
SS = DOS DS
Return: DS = DOS DS
Note:   called by DOS 4.0 kernel on INT 21/AX=5702h,INT 21/AX=5703h,
INT 21/AX=5704h


2F112D - IFSFUNC.EXE (DOS 4.x only) - ???