MXS-2008 Provide single entrypoint for initializing maxbase

Everything of maxbase can now be initialized by a call to

    maxbase_init();

(from a C-program) or

    maxbase::init();

from a C++-program and finalized with calls to either
maxbase_finish() or maxbase::finish(). Creating an instance
maxbase::MaxBase will take care of both operations.

maxutils/maxbase/include/maxbase/messagequeue.hh

@@ -18,6 +18,7 @@
 namespace maxbase
 {
 
+class MaxBase;
 class MessageQueue;
 class Worker;
 
@@ -116,21 +117,6 @@ public:
     typedef MessageQueueHandler Handler;
     typedef MessageQueueMessage Message;
 
-    /**
-     * Initializes the message queue mechanism. To be called once at
-     * process startup.
-     *
-     * @return True if the initialization succeeded, false otherwise.
-     */
-    static bool init();
-
-
-    /**
-     * Finalizes the message queue mechanism. To be called once at
-     * process shutdown, if the initialization succeeded.
-     */
-    static void finish();
-
     /**
      * Creates a @c MessageQueue with the provided handler.
      *
@@ -190,6 +176,12 @@ public:
      */
     Worker* remove_from_worker();
 
+public:
+    // TODO: Make private once all callers have been modified.
+    friend class MaxBase;
+    static bool init();
+    static void finish();
+
 private:
     MessageQueue(Handler* pHandler, int read_fd, int write_fd);