INT 61 - PC/TCP kernel v2.05+ - "net_flush" - FLUSH PENDING DATA
        AH = 1Eh
        BX = network descriptor
Return: CF clear if successful
        CF set on error
            AX = error code (see INT 61"PC/TCP")
Notes:  bufferred data is transmitted immediately, overriding Nagle's algorithm
          if necessary
        this function is not supported by Beame&Whiteside's BWPCTCP v3.0a shim
SeeAlso: INT 61"PC/TCP",INT 61/AH=00h"PC/TCP"

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