[raknet] Add ReliabilityLayer ctor as stub

* Adds `ReliabilityLayer::InitializeVariable()` stub

raknet/ReliabilityLayer.cpp

@@ -0,0 +1,15 @@
+// TODO: Implement ReliabilityLayer.cpp
+
+#include "ReliabilityLayer.h"
+
+ReliabilityLayer::ReliabilityLayer()
+{
+	// TODO: ReliabilityLayer::ReliabilityLayer
+
+	InitializeVariables();
+}
+
+void ReliabilityLayer::InitializeVariables( void )
+{
+	// TODO: ReliabilityLayer::InitializeVariables
+}