lib/nfs/Manager: gcc 4.7 compatibility hack

std::map::emplace() is only available from gcc 4.8 on.

src/lib/nfs/Connection.hxx

@@ -103,6 +103,22 @@ public:
 		 server(_server), export_name(_export_name),
 		 context(nullptr) {}
 
+#if defined(__GNUC__) && !defined(__clang__) && !GCC_CHECK_VERSION(4,8)
+	/* needed for NfsManager::GetConnection() due to lack of
+	   std::map::emplace() */
+	NfsConnection(NfsConnection &&other)
+		:SocketMonitor(((SocketMonitor &)other).GetEventLoop()),
+		 DeferredMonitor(((DeferredMonitor &)other).GetEventLoop()),
+		 server(std::move(other.server)),
+		 export_name(std::move(other.export_name)),
+		 context(nullptr) {
+		assert(other.context == nullptr);
+		assert(other.new_leases.empty());
+		assert(other.active_leases.empty());
+		assert(other.callbacks.IsEmpty());
+	}
+#endif
+
 	~NfsConnection();
 
 	gcc_pure

src/lib/nfs/Manager.cxx

@@ -39,10 +39,19 @@ NfsManager::GetConnection(const char *server, const char *export_name)
 
 	const std::string key = Key(server, export_name);
 
+#if defined(__GNUC__) && !defined(__clang__) && !GCC_CHECK_VERSION(4,8)
+	/* std::map::emplace() not available; this hack uses the move
+	   constructor */
+	auto e = connections.insert(std::make_pair(key,
+						   ManagedConnection(*this, loop,
+								     server,
+								     export_name)));
+#else
 	auto e = connections.emplace(std::piecewise_construct,
 				     std::forward_as_tuple(key),
 				     std::forward_as_tuple(*this, loop,
 							   server,
 							   export_name));
+#endif
 	return e.first->second;
 }

src/lib/nfs/Manager.hxx

@@ -41,6 +41,13 @@ class NfsManager {
 			:NfsConnection(_loop, _server, _export_name),
 			 manager(_manager) {}
 
+#if defined(__GNUC__) && !defined(__clang__) && !GCC_CHECK_VERSION(4,8)
+		/* needed due to lack of std::map::emplace() */
+		ManagedConnection(ManagedConnection &&other)
+			:NfsConnection(std::move(other)),
+			 manager(other.manager) {}
+#endif
+
 	protected:
 		/* virtual methods from NfsConnection */
 		void OnNfsConnectionError(Error &&error) override;