Refactor: BLI_path_util (split out app directory access)

This module is intended for path manipulation functions
but had utility functions added to access various directories.

source/blender/windowmanager/intern/wm_files.c

@@ -69,6 +69,7 @@
 #include "DNA_screen_types.h"
 #include "DNA_windowmanager_types.h"
 
+#include "BKE_appdir.h"
 #include "BKE_utildefines.h"
 #include "BKE_autoexec.h"
 #include "BKE_blender.h"