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/worker.hh

@@ -559,22 +559,6 @@ public:
         };
     };
 
-    /**
-     * Initialize the worker mechanism.
-     *
-     * To be called once at process startup.
-     *
-     * @return True if the initialization succeeded, false otherwise.
-     */
-    static bool init();
-
-    /**
-     * Finalize the worker mechanism.
-     *
-     * To be called once at process shutdown.
-     */
-    static void finish();
-
     enum
     {
         MAX_EVENTS = 1000
@@ -990,6 +974,11 @@ protected:
      */
     static void resolve_poll_error(int fd, int err, int op);
 
+public:
+    // TODO: Make private once all callers have beed modified.
+    static bool init();
+    static void finish();
+
 private:
     class DelayedCall;
     friend class DelayedCall;