config: file: Mark config_CreateDir as static

It's not in any other file

src/config/configuration.h

@@ -27,7 +27,6 @@ extern "C" {
 
 /* Internal configuration prototypes and structures */
 
-int  config_CreateDir( vlc_object_t *, const char * );
 int  config_AutoSaveConfigFile( vlc_object_t * );
 
 void config_Free (module_config_t *, size_t);

src/config/file.c

@@ -267,7 +267,7 @@ int config_LoadConfigFile( vlc_object_t *p_this )
 /*****************************************************************************
  * config_CreateDir: Create configuration directory if it doesn't exist.
  *****************************************************************************/
-int config_CreateDir( vlc_object_t *p_this, const char *psz_dirname )
+static int config_CreateDir( vlc_object_t *p_this, const char *psz_dirname )
 {
     if( !psz_dirname || !*psz_dirname ) return -1;