Added workaround for Safari CORS bug (#183)

Frontend/speedtest_worker.js

@@ -130,6 +130,10 @@ this.addEventListener('message', function (e) {
 		//Chrome mobile introduced a limitation somewhere around version 65, we have to limit XHR upload size to 4 megabytes
 		settings.xhr_ul_blob_megabytes=4;
 	  }
+	  if (/^((?!chrome|android|crios|fxios).)*safari/i.test(ua)) {
+        //Safari also needs the IE11 workaround but only for the MPOT version
+        settings.forceIE11Workaround = true
+      }
       //telemetry_level has to be parsed and not just copied
       if(typeof s.telemetry_level !== 'undefined') settings.telemetry_level = s.telemetry_level === 'basic' ? 1 : s.telemetry_level === 'full' ? 2 : s.telemetry_level === 'debug' ? 3 : 0; // telemetry level
       //transform test_order to uppercase, just in case