The SMB$READ_MESSAGE_ITEM routine reads a buffer that was filled
    in by the SMB$READ_MESSAGE routine, parses one message item from
    the buffer, writes the item's code into a longword, and writes
    the item into a buffer.

    Format

      SMB$READ_MESSAGE_ITEM  message ,context ,item_code ,buffer

                             [,size]

  Additional Information (explode) :

• Returns
• Arguments
• Description
• Codes for Message Items
• Condition Values Returned