- the correct registry location to override is User Shell Folders, not
  Shell Folders
- if User Shell Folders doesn't exist in HKCU, HKLM should be tried
- SHGetSpecialFolderPath should call SHGetFolderPath, not vice-versa
- the default values should be localizable
- some of the parameter checking and returned LPITEMIDLISTs were a bit
  off

diff --git a/include/winuser.h b/include/winuser.h
index 9a242c2..79782f0 100644
--- a/include/winuser.h
+++ b/include/winuser.h
@@ -513,6 +513,7 @@
 
 /***** Dialogs *****/
 
+#define IS_INTRESOURCE(x)   (((ULONG_PTR)(x) >> 16) == 0)
 #define MAKEINTRESOURCEA(i) (LPSTR)((ULONG_PTR)((WORD)(i)))
 #define MAKEINTRESOURCEW(i) (LPWSTR)((ULONG_PTR)((WORD)(i)))