aggregate.m: compatibility fix for MATLAB R2014a

The importdata function returns empty lines on R2014a, while it omits them in
R2020a. Moreover, importdata is not meant to parse arbitrary text file. We thus
replace it by repeated calls to fgetl.

matlab/aggregate.m

@@ -63,7 +63,17 @@ eqlist = cell(MAX_NUMBER_OF_ELEMENTS, 4);
 tagnum = 1;
 eqnum = 0;
 for i=1:length(varargin)
-    model = importdata(sprintf('%s/model.inc', varargin{i}));
+    % Store all non-empty lines of model.inc in the “model” cell-array
+    fid = fopen(sprintf('%s/model.inc', varargin{i}));
+    model = {};
+    while ~feof(fid)
+        line = fgetl(fid);
+        if ~isempty(line)
+            model{end+1} = line;
+        end
+    end
+    fclose(fid);
+
     eqtag = false;
     for j=1:length(model)
         if isequationtag(model{j})