include: Add SM_CXPADDEDBORDER to winuser.h.

include/winuser.h

@@ -982,6 +982,7 @@ WINUSERAPI BOOL     WINAPI SetSysColors(INT,const INT*,const COLORREF*);
 #define SM_SERVERR2           89
 #define SM_CMETRICS           90
 #define SM_MOUSEHORIZONTALWHEELPRESENT 91
+#define SM_CXPADDEDBORDER     92
 
 #define SM_REMOTESESSION        0x1000
 #define SM_SHUTTINGDOWN         0x2000