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