INT 21 - LANtastic v3+ - GET ACCOUNT
        AX = 5F87h
        DS:SI -> 128-byte buffer for account information (see below)
        ES:DI -> ASCIZ machine name in form "\\machine"
Return: CF clear if successful
        CF set on error
            AX = error code
        BX destroyed
Note:   must be logged into the specified machine

Format of user account structure:
Offset  Size    Description
 00h 16 BYTEs   blank-padded username (zero-padded for v4.x)
 10h 16 BYTEs   reserved (00h)
 20h 32 BYTEs   user description
 40h    BYTE    privilege bits (see below)
 41h    BYTE    maximum concurrent users
 42h 42 BYTEs   bit map for disallowed half hours, beginning on Sunday
                (bit set if half-hour not an allowed time)
 6Ch    WORD    internal (0002h)
 6Eh  2 WORDs   last login time
 72h  2 WORDs   account expiration date (MS-DOS-format year/month:day)
 76h  2 WORDs   password expiration date (0 = none)
 7Ah    BYTE    number of days to extend password after change (1-31)
                00h if no extension required
---v3.x---
 7Bh  5 BYTEs   reserved
---v4.x---
 7Bh    BYTE    storage for first letter of user name when deleted (first
                character is changed to 00h when deleting account)
 7Ch    BYTE    extended privileges
 7Dh  3 BYTEs   reserved

Bitfields for privilege bits:
 bit 7  bypass access control lists
 bit 6  bypass queue protection
 bit 5  treat as local process
 bit 4  bypass mail protection
 bit 3  allow audit entry creation
 bit 2  system manager
 bit 0  user cannot change password

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