Fix typo.

Doc/ext/windows.tex

@@ -163,8 +163,8 @@ Hello, world
     click OK.  (Inserting them one by one is fine too.)
 
     Now open the \menuselection{Project \sub spam properties} dialog.
-    You only need to change a few settings.  Make sure \guilable{All
-    Configurations} is selected from the \guilable{Settings for:}
+    You only need to change a few settings.  Make sure \guilabel{All
+    Configurations} is selected from the \guilabel{Settings for:}
     dropdown list.  Select the C/\Cpp{} tab.  Choose the General
     category in the popup menu at the top.  Type the following text in
     the entry box labeled \guilabel{Additional Include Directories}: