Fix a typo.

include/oleidl.idl

diff --git a/include/oleidl.idl b/include/oleidl.idl
index 5e41081..4e7670c 100644
--- a/include/oleidl.idl
+++ b/include/oleidl.idl
@@ -252,7 +252,7 @@
         [in, out] LPOLEINPLACEFRAMEINFO lpFrameInfo);
 
     HRESULT Scroll(
-        [in] SIZE scrollExtant);
+        [in] SIZE scrollExtent);
 
     HRESULT OnUIDeactivate(
         [in] BOOL fUndoable);