Path finding fixes:

Track path finding and order book creation time and latency.
Use a ledger snapshot for path finding.
You can't call getCurrentLedger from an unlocked context.
Pathfinding called from the transaction sign function held the master lock.

src/cpp/ripple/OrderBook.h

@@ -1,3 +1,8 @@
+
+#ifndef ORDERBOOK_H
+#define ORDERBOOK_H
+
+
 #include "SerializedLedger.h"
 #include "NetworkOPs.h"
 #include <boost/shared_ptr.hpp>
@@ -34,4 +39,6 @@ public:
 	STAmount& getTakePrice(STAmount& takeAmount);
 };
 
+#endif
+
 // vim:ts=4