conf: added the gcc "const" attribute to some functions

src/conf.h

@@ -101,6 +101,7 @@ struct config_param {
  * A GQuark for GError instances, resulting from malformed
  * configuration.
  */
+G_GNUC_CONST
 static inline GQuark
 config_quark(void)
 {
@@ -120,15 +121,18 @@ void config_read_file(const char *file);
 
 /* don't free the returned value
    set _last_ to NULL to get first entry */
+G_GNUC_CONST
 struct config_param *
 config_get_next_param(const char *name, const struct config_param *last);
 
+G_GNUC_CONST
 static inline struct config_param *
 config_get_param(const char *name)
 {
 	return config_get_next_param(name, NULL);
 }
 
+G_GNUC_CONST
 const char *
 config_get_string(const char *name, const char *default_value);
 
@@ -137,21 +141,27 @@ config_get_string(const char *name, const char *default_value);
  * absolute path.  If there is a tilde prefix, it is expanded.  Aborts
  * MPD if the path is not a valid absolute path.
  */
+G_GNUC_CONST
 const char *
 config_get_path(const char *name);
 
+G_GNUC_CONST
 unsigned
 config_get_positive(const char *name, unsigned default_value);
 
+G_GNUC_CONST
 struct block_param *
 config_get_block_param(const struct config_param *param, const char *name);
 
+G_GNUC_CONST
 bool config_get_bool(const char *name, bool default_value);
 
+G_GNUC_CONST
 const char *
 config_get_block_string(const struct config_param *param, const char *name,
 			const char *default_value);
 
+G_GNUC_CONST
 static inline char *
 config_dup_block_string(const struct config_param *param, const char *name,
 			const char *default_value)
@@ -159,14 +169,17 @@ config_dup_block_string(const struct config_param *param, const char *name,
 	return g_strdup(config_get_block_string(param, name, default_value));
 }
 
+G_GNUC_CONST
 unsigned
 config_get_block_unsigned(const struct config_param *param, const char *name,
 			  unsigned default_value);
 
+G_GNUC_CONST
 bool
 config_get_block_bool(const struct config_param *param, const char *name,
 		      bool default_value);
 
+G_GNUC_CONST
 struct config_param *
 config_new_param(const char *value, int line);