peer: fix struct alignment

Integers used atomically MUST be aligned properly, otherwise the
sync library will crash on purpose. Therefore non-aligned struct
members must come later.

peer.go

@@ -114,8 +114,6 @@ type peer struct {
 	started    int32
 	disconnect int32
 
-	cfg *Config
-
 	// The following fields are only meant to be used *atomically*
 	bytesReceived uint64
 	bytesSent     uint64
@@ -130,6 +128,8 @@ type peer struct {
 	// our last ping message.  To be used atomically.
 	pingLastSend int64
 
+	cfg *Config
+
 	connReq *connmgr.ConnReq
 	conn    net.Conn