Add [process|thread] [init|finish] functions to modules

The MXS_MODULDE object now contains optinal pointers for functions
to be called att process and thread startup and shutdown. Since the
functions were added to the end, strictly speaking, all structures
would not have needed to have been modified, but better to be
explicit. In a subsequent change, these will be called.

C++ does not support flexible arrays, so for the time being C++
modules are restricted to 10 parameters. Better approach is to
factor out the parameters to a separate array and then just store
a pointer to that array in MXS_MODULE.

include/maxscale/modinfo.h

@@ -14,14 +14,6 @@
 
 /**
  * @file modinfo.h The module information interface
- *
- * @verbatim
- * Revision History
- *
- * Date     Who             Description
- * 02/06/14 Mark Riddoch    Initial implementation
- *
- * @endverbatim
  */
 
 #include <maxscale/cdefs.h>
@@ -114,15 +106,53 @@ typedef struct mxs_module_param
 /**
  * The module information structure
  */
-typedef struct
+typedef struct mxs_module
 {
     MXS_MODULE_API      modapi;        /**< Module API type */
     MXS_MODULE_STATUS   status;        /**< Module development status */
     MXS_MODULE_VERSION  api_version;   /**< Module API version */
-    const char     *description;   /**< Module description */
-    const char     *version;       /**< Module version */
-    void           *module_object; /**< Module type specific API implementation */
-    MXS_MODULE_PARAM parameters[]; /**< Declared parameters */
+    const char         *description;   /**< Module description */
+    const char         *version;       /**< Module version */
+    void               *module_object; /**< Module type specific API implementation */
+    /**
+     * If non-NULL, this function is called once at process startup. If the
+     * function fails, MariaDB MaxScale will not start.
+     *
+     * @return 0 on success, non-zero on failure.
+     */
+    int (*init)();
+
+    /**
+     * If non-NULL, this function is called once at process shutdown, provided
+     * the call to @c init succeeded.
+     */
+    void (*finish)();
+
+    /**
+     * If non-NULL, this function is called once at the startup of every new thread.
+     * If the function fails, then the thread will terminate.
+     *
+     * @attention This function is *not* called for the thread where @c init is called.
+     *
+     * @return 0 on success, non-zero on failure.
+     */
+    int (*thread_init)();
+
+    /**
+     * If non-NULL, this function is called when a thread terminates, provided the
+     * call to @c thread_init succeeded.
+     *
+     * @attention This function is *not* called for the thread where @c init is called.
+     */
+    void (*thread_finish)();
+
+#ifdef __cplusplus
+    // TODO: C++ does not have flexible arrays, so for the time being C++ modules
+    // TODO: are restricted to 10 parameters.
+    MXS_MODULE_PARAM parameters[11];  /**< Declared parameters */
+#else
+    MXS_MODULE_PARAM parameters[];  /**< Declared parameters */
+#endif
 } MXS_MODULE;
 
 /**