Workaround for a strange bug with Octave.

If there is any call to exist(fname) before the call to the preprocessor, then
Octave will use the old copy of the .m instead of the newly generated one.
Deleting the .m beforehand fixes the problem.
(cherry picked from commit c3918761)

matlab/dynare.m

@@ -96,6 +96,14 @@ else
     end;
 end;
 
+% Workaround for a strange bug with Octave: if there is any call to exist(fname)
+% before the call to the preprocessor, then Octave will use the old copy of
+% the .m instead of the newly generated one. Deleting the .m beforehand
+% fixes the problem.
+if isoctave && length(dir([fname(1:(end-4)) '.m'])) > 0
+    delete([fname(1:(end-4)) '.m'])
+end
+
 if ~isempty(strfind(fname,filesep))
     fprintf('\nIt seems you are trying to call a mod-file not located in the "Current Folder". This is not possible (the %s symbol is not allowed in the name of the mod file).\n', filesep)
     [pathtomodfile,basename,ext] = fileparts(fname);