Set trace destination

        Entry:
          AH = FEh
          AL = trace destinations
              bit 0  storage (DS:DX -> trace stats record)
              bit 1  display
              bit 2  file (trace written to file OUTPUT.PC)
              bit 3  printer

        Format of Trace Statistics Record:

        Offset  Size    Description
         00h    DWORD   pointer to storage trace buffer
         04h    WORD    max number of 80-byte records in trace
         06h    WORD    (high-order byte first!) current record number (must init to 0)
         08h    DWORD   (high-order byte first!) number of records written (init to 0)
         0Ch    DWORD   reserved

        Note: do not move record while trace is active