INT 2F CU - NETWORK REDIRECTOR (DOS 4+) - EXTENDED OPEN/CREATE FILE
        AX = 112Eh
        SS = DS = DOS DS
        ES:DI -> uninitialized SFT for file
        STACK: WORD file attribute for created/truncated file
                        low byte = file attributes
                        high byte = 00h normal create/open, 01h create new file
        SDA first filename pointer -> fully-qualified filename
        SDA extended file open action = action code (see INT 21/AX=6C00h)
        SDA extended file open mode = open mode for file (see INT 21/AX=6C00h)
Return: CF set on error
            AX = error code
        CF clear if successful
            CX = result code
                01h file opened
                02h file created
                03h file replaced (truncated)
            SFT initialized (except handle count, which DOS manages itself)
Note:   this function is called by the DOS 4+ kernel
SeeAlso: AX=1115h,AX=1116h,AX=1117h,INT 21/AX=6C00h

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