Forward declare in a few places

src/base/bittorrent/peerinfo.h

@@ -31,10 +31,11 @@
 
 #include <libtorrent/peer_info.hpp>
 
-#include <QBitArray>
 #include <QCoreApplication>
 #include <QHostAddress>
 
+class QBitArray;
+
 namespace BitTorrent
 {
     class TorrentHandle;