Add framework for declaration of module parameters

The MXS_MODULE structure now contains a member for parameters. This can be
used by the modules to declare accepted parameters, their types and the
default values. Currently only count, integer, boolean, string and enum
values are supported.

include/maxscale/modinfo.h

@@ -76,6 +76,24 @@ typedef struct
     int     patch;
 } MXS_MODULE_VERSION;
 
+enum mxs_module_param_type
+{
+    MXS_MODULE_PARAM_COUNT, /**< Non-negative number */
+    MXS_MODULE_PARAM_INT, /**< Integer number */
+    MXS_MODULE_PARAM_BOOL, /**< Boolean value */
+    MXS_MODULE_PARAM_STRING, /**< String value */
+    MXS_MODULE_PARAM_ENUM /**< Enumeration of string values */
+};
+
+/** Module parameter declaration */
+typedef struct mxs_module_param
+{
+    const char *name; /**< Name of the parameter */
+    enum mxs_module_param_type type; /**< Type of the parameter */
+    const char *default_value;
+    const char **accepted_values; /**< Only for enum values */
+} MXS_MODULE_PARAM;
+
 /**
  * The module information structure
  */
@@ -87,8 +105,15 @@ typedef struct
     const char     *description;   /**< Module description */
     const char     *version;       /**< Module version */
     void           *module_object; /**< Module type specific API implementation */
+    MXS_MODULE_PARAM parameters[]; /**< Declared parameters */
 } MXS_MODULE;
 
+/**
+ * This should be the last value given to @c parameters. If the module has no
+ * parameters, it should be the only value.
+ */
+#define MXS_END_MODULE_PARAMS .name = NULL
+
 /**
  * Name of the module entry point
  *