Use std::bind instead of boost::bind to re-lock the wallet

Change suggested by Marco Falke.

Author: sdaftuar

src/wallet/rpcwallet.cpp

@@ -37,6 +37,8 @@
 
 #include <univalue.h>
 
+#include <functional>
+
 static const std::string WALLET_ENDPOINT_BASE = "/wallet/";
 
 CWallet *GetWalletForJSONRPCRequest(const JSONRPCRequest& request)
@@ -2402,7 +2404,7 @@ UniValue walletpassphrase(const JSONRPCRequest& request)
     pwallet->TopUpKeyPool();
 
     pwallet->nRelockTime = GetTime() + nSleepTime;
-    RPCRunLater(strprintf("lockwallet(%s)", pwallet->GetName()), boost::bind(LockWallet, pwallet), nSleepTime);
+    RPCRunLater(strprintf("lockwallet(%s)", pwallet->GetName()), std::bind(LockWallet, pwallet), nSleepTime);
 
     return NullUniValue;
 }