% TTRETRIEVE   Retrieve a fetched message from a mailbox%%  Usage: msg = ttRetrieve(mailboxname)%%  Inputs:%    mailboxname  Name of a mailbox.%%  Note:%    The message must have been fetched in a previous code segment%    using TTFETCH.%       % See also TTCREATEMAILBOX, TTTRYPOST, TTTRYFETCH, TTPOST, TTFETCH%%       TrueTime, Version 1.4%       Copyright (c) 2006%       Martin Ohlin, Dan Henriksson and Anton Cervin%       Department of Automatic Control, LTH%       Lund University, Sweden