HintRouter: Support various hint types, round-robin rotate slaves

Supports hint types:
-master
-slave
-named server
-all

A default action, which is performed when no hint exists or on error,
can be set. The different actions are analogous to the hint types.

A maximum connection number for slaves can be set. If more slaves are
configured for the service, the filter will rotate slaves for new sessions.

Within a session with multiple slaves, the "route_to_slave"-hint will
also rotate among the slave backends.

server/modules/routing/hintrouter/hintrouter.hh

@@ -13,6 +13,7 @@
  */
 
 #include "hintrouterdefs.hh"
+
 #include <maxscale/router.hh>
 #include "hintroutersession.hh"
 
@@ -20,15 +21,25 @@ class HintRouter : public maxscale::Router<HintRouter, HintRouterSession>
 {
 public:
     static HintRouter* create(SERVICE* pService, char** pzOptions);
-
     HintRouterSession* newSession(MXS_SESSION *pSession);
-
     void diagnostics(DCB* pOut);
-
     uint64_t getCapabilities();
-
+    HINT_TYPE get_default_action() const
+    {
+        return m_default_action;
+    };
+    const string& get_default_server() const
+    {
+        return m_default_server;
+    };
 private:
-    HintRouter(SERVICE* pService);
+    HintRouter(SERVICE* pService, HINT_TYPE default_action, string& default_server,
+               int max_slaves);
+
+    HINT_TYPE m_default_action;
+    string m_default_server;
+    int m_max_slaves;
+    volatile int m_total_slave_conns;
 
 private:
     HintRouter(const HintRouter&);