INT 14 - FOSSIL - ENABLE/DISABLE FLOW CONTROL
        AH = 0Fh
        AL = bit mask describing requested flow control (see below)
        DX = port number
SeeAlso: AH=09h"MBBIOS",AH=10h"FOSSIL"

Bitfields for requested flow control:
 bit 0  XON/XOFF on transmit (watch for XOFF while sending)
 bit 1  CTS/RTS (CTS on transmit/RTS on receive)
 bit 2  reserved
 bit 3  XON/XOFF on receive (send XOFF when buffer near full)
 bit 4-7 all 1

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