shell32: Add a stub for LinkWindow_UnregisterClass.

dlls/shell32/shell32.spec

@@ -211,6 +211,7 @@
  251 stdcall -noname PathRemoveArgs(ptr) PathRemoveArgsAW
  256 stdcall @(ptr ptr) SHELL32_256
  258 stdcall -noname LinkWindow_RegisterClass()
+ 259 stdcall -noname LinkWindow_UnregisterClass()
 #299 stub Shl1632_ThunkData32
 #300 stub Shl3216_ThunkData32
 

dlls/shell32/shellord.c

@@ -1966,3 +1966,12 @@ BOOL WINAPI LinkWindow_RegisterClass(void)
     FIXME("()\n");
     return TRUE;
 }
+
+/*************************************************************************
+ *              LinkWindow_UnregisterClass (SHELL32.259)
+ */
+BOOL WINAPI LinkWindow_UnregisterClass(void)
+{
+    FIXME("()\n");
+    return TRUE;
+}