backport fix build for clang

Destination.cpp

@@ -527,7 +527,7 @@ namespace client
 	{
 		if (!m_Pool || !IsReady ()) 
 		{	
-			if (requestComplete) requestComplete (false);
+			if (requestComplete) requestComplete (nullptr);
 			return false;
 		}	
 		m_Service.post (std::bind (&ClientDestination::RequestLeaseSet, shared_from_this (), dest, requestComplete));
@@ -630,7 +630,7 @@ namespace client
 				
 				if (done)
 				{
-					if (it->second->requestComplete) it->second->requestComplete (false);
+					if (it->second->requestComplete) it->second->requestComplete (nullptr);
 					delete it->second;
 					m_LeaseSetRequests.erase (it);
 				}	

Log.cpp

@@ -24,7 +24,7 @@ void LogMsg::Process()
 
 const std::string& Log::GetTimestamp ()
 {
-#if (__GNUC__ == 4) && (__GNUC_MINOR__ <= 6)	
+#if (__GNUC__ == 4) && (__GNUC_MINOR__ <= 6) && !defined(__clang__)	
 	auto ts = std::chrono::monotonic_clock::now ();	
 #else	
 	auto ts = std::chrono::steady_clock::now ();	

Log.h

@@ -50,7 +50,7 @@ class Log: public i2p::util::MsgQueue<LogMsg>
 		
 		std::ostream * m_LogStream;
 		std::string m_Timestamp;
-#if (__GNUC__ == 4) && (__GNUC_MINOR__ <= 6) // gcc 4.6
+#if (__GNUC__ == 4) && (__GNUC_MINOR__ <= 6) && !defined(__clang__) // gcc 4.6
 		std::chrono::monotonic_clock::time_point m_LastTimestampUpdate;
 #else		
 		std::chrono::steady_clock::time_point m_LastTimestampUpdate;