Fix possible folder watching issues on Windows

src/filesystemwatcher.h

@@ -203,7 +203,11 @@ private:
   void addTorrentsFromDir(const QDir &dir, QStringList &torrents) {
     const QStringList files = dir.entryList(filters, QDir::Files, QDir::Unsorted);
     foreach(const QString &file, files) {
-      torrents << dir.canonicalPath() + '/' + file;
+#if defined(Q_WS_WIN) || defined(Q_OS_OS2)
+      torrents << dir.absoluteFilePath(file).replace("/", "\\");
+#else
+      torrents << dir.absoluteFilePath(file);
+#endif
     }
   }