scripted-diff: Use the C++11 keyword nullptr to denote the pointer literal instead of the macro NULL

-BEGIN VERIFY SCRIPT-
sed -i 's/\<NULL\>/nullptr/g' src/*.cpp src/*.h src/*/*.cpp src/*/*.h src/qt/*/*.cpp src/qt/*/*.h src/wallet/*/*.cpp src/wallet/*/*.h src/support/allocators/*.h
sed -i 's/Prefer nullptr, otherwise SAFECOOKIE./Prefer NULL, otherwise SAFECOOKIE./g' src/torcontrol.cpp
sed -i 's/tor: Using nullptr authentication/tor: Using NULL authentication/g' src/torcontrol.cpp
sed -i 's/METHODS=nullptr/METHODS=NULL/g' src/test/torcontrol_tests.cpp src/torcontrol.cpp
sed -i 's/nullptr certificates/NULL certificates/g' src/qt/paymentserver.cpp
sed -i 's/"nullptr"/"NULL"/g' src/torcontrol.cpp src/test/torcontrol_tests.cpp
-END VERIFY SCRIPT-

src/rpc/server.cpp

@@ -30,7 +30,7 @@ static bool fRPCInWarmup = true;
 static std::string rpcWarmupStatus("RPC server started");
 static CCriticalSection cs_rpcWarmup;
 /* Timer-creating functions */
-static RPCTimerInterface* timerInterface = NULL;
+static RPCTimerInterface* timerInterface = nullptr;
 /* Map of name to timer. */
 static std::map<std::string, std::unique_ptr<RPCTimerBase> > deadlineTimers;
 
@@ -301,7 +301,7 @@ const CRPCCommand *CRPCTable::operator[](const std::string &name) const
 {
     std::map<std::string, const CRPCCommand*>::const_iterator it = mapCommands.find(name);
     if (it == mapCommands.end())
-        return NULL;
+        return nullptr;
     return (*it).second;
 }
 
@@ -547,7 +547,7 @@ void RPCSetTimerInterface(RPCTimerInterface *iface)
 void RPCUnsetTimerInterface(RPCTimerInterface *iface)
 {
     if (timerInterface == iface)
-        timerInterface = NULL;
+        timerInterface = nullptr;
 }
 
 void RPCRunLater(const std::string& name, std::function<void(void)> func, int64_t nSeconds)