INT 61 - PC/TCP kernel v2.05+ - "net_getglobdesc" - ALLOCATE GLOBAL DESCRIPTOR
        AH = 29h
Return: CF clear if successful
            AX = network descriptor
        CF set on error
            AX = error code (see INT 61"PC/TCP")
Note:   use this function rather than AH=22h to avoid a DOS call by the PC/TCP
          kernel; the returned descriptor will be >= 40h and cannot be used
          with "net_select" (AH=0Eh)
SeeAlso: INT 61"PC/TCP",INT 61/AH=00h"PC/TCP",INT 61/AH=07h"PC/TCP"
SeeAlso: INT 61/AH=22h

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