Accessibility : Make the closing button more explicit.

add a aria-describedby to link the buton to the title of the combo to
make the 7.1 criterion of the RGAA 4.1 pass

7.1 : The HTML generated by the script should be compatible with
accessibility technology.

Here, the button was not sufficiently explicit, making potentially
someone wonder what would be closed by this button.

tarteaucitron.js

@@ -494,9 +494,9 @@ var tarteaucitron = {
                 }
                 html += '<div id="tarteaucitron" role="dialog" aria-modal="true" aria-labelledby="dialogTitle" tabindex="-1">';
                 if (tarteaucitron.reloadThePage) {
-                    html += '   <button type="button" id="tarteaucitronClosePanel" aria-label="' + tarteaucitron.lang.close + ' (' + tarteaucitron.lang.reload + ')" title="' + tarteaucitron.lang.close + ' (' + tarteaucitron.lang.reload + ')">';
+                    html += '   <button type="button" id="tarteaucitronClosePanel" aria-describedby="dialogTitle" aria-label="' + tarteaucitron.lang.close + ' (' + tarteaucitron.lang.reload + ')" title="' + tarteaucitron.lang.close + ' (' + tarteaucitron.lang.reload + ')">';
                 } else {
-                    html += '   <button type="button" id="tarteaucitronClosePanel">';
+                    html += '   <button type="button" id="tarteaucitronClosePanel" aria-describedby="dialogTitle" >';
                 }
                 html += '       ' + tarteaucitron.lang.close;
                 html += '   </button>';