Revert "Deleted size overloaded function."

This reverts commit fbc36e39.

src/@dates/size.m

+function varargout = size(o)
+
+% Copyright (C) 2013 -2014 Dynare Team
+%
+% This file is part of Dynare.
+%
+% Dynare is free software: you can redistribute it and/or modify
+% it under the terms of the GNU General Public License as published by
+% the Free Software Foundation, either version 3 of the License, or
+% (at your option) any later version.
+%
+% Dynare is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with Dynare.  If not, see <http://www.gnu.org/licenses/>.
+
+switch nargout
+  case 0
+    if isempty(o)
+        size([])
+    else
+        size(o.time)
+    end
+  case 1
+    if isempty(o)
+        varargout{1} = size([]);
+    else
+        varargout{1} = size(o.time);
+    end
+  otherwise
+    error('dates::size: Wrong calling sequence! Cannot return more than one argument.')
+end
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