Add workaround for issues with GPX generation in IE11

This works around JXON issue Project-OSRM#42 [1] by repairing the invalid XML name
space declarations in the GPX data and should thus yield usable GPX files
in IE11, too.

[1] tyrasd/jxon#42

src/tools.js

@@ -110,6 +110,10 @@ var Control = L.Control.extend({
   _downloadGPX: function() {
     if (this.routeGeoJSON) {
       var gpxData = togpx(this.routeGeoJSON);
+      // Work around issues with XML name space generation in IE 11
+      // (see also https://github.com/tyrasd/jxon/issues/42)
+      gpxData = gpxData.replace(/\s+xmlns:NS\d=""/g, '');
+      gpxData = gpxData.replace(/NS\d:/g, '');
       var blob = new Blob([gpxData], {
         type: 'application/gpx+xml;charset=utf-8'
       }, false);