Remove all trailing spaces

No real changes, just clean up sources by removing trailing spaces from
all the non-generated files.

This should hopefully avoid future commits mixing significant changes
with insignificant whitespace ones.

interface/wx/treectrl.h

@@ -185,7 +185,7 @@ public:
             Window position.
             If ::wxDefaultPosition is specified then a default position is chosen.
         @param size
-            Window size. 
+            Window size.
             If ::wxDefaultSize is specified then the window is sized appropriately.
         @param style
             Window style. See wxTreeCtrl.
@@ -470,7 +470,7 @@ public:
         Returns the item last clicked or otherwise selected.
         Unlike GetSelection(), it can be used whether or not
         the control has the @c wxTR_MULTIPLE style.
-        
+
         @since 2.9.1
     */
     virtual wxTreeItemId GetFocusedItem() const;
@@ -647,7 +647,7 @@ public:
     /**
         Returns the selection, or an invalid item if there is no selection. This
         function only works with the controls without @c wxTR_MULTIPLE style,
-        use GetSelections() for the controls which do have this style 
+        use GetSelections() for the controls which do have this style
         or, if a single item is wanted, use GetFocusedItem().
     */
     virtual wxTreeItemId GetSelection() const;