Extended Open/Create (INT 21h, 6Ch)

        Optionally opens and creates a file.

        Entry:
          AX = 6C00h
          BX = Mode
                 1xx1 1111 xxxx 1xxx  Reserved - Must be zero
                 x1xx xxxx xxxx xxxx  0=Commit, 1=Auto Commit on write
                 xx1x xxxx xxxx xxxx  1=Disable INT 24h for this handle
                 xxxx xxxx 1xxx xxxx  0=Pass handle to child, 1=Don't pass
                 xxxx xxxx x111 xxxx  Sharing mode
                                        000 = Compatibility
                                        001 = Deny Read/Write
                                        010 = Deny Write
                                        011 = Deny Read
                                        100 = Deny None
                 xxxx xxxx xxxx x111  Access code
                                        000 = Read
                                        001 = Write
                                        010 = Read/Write