Add missing references to wxSize parameters in wxBitmapBundle

Pass wxSize by const reference instead of "const" value.

Note that passing wxSize by value might be not such a bad thing,
actually, but we use const reference for it everywhere else, so do it
here as well for consistency (and the original intention was to do it
like this, missing "&" was just a typo subsequently propagated through
copy-pasting).

No real changes.

interface/wx/bmpbndl.h

@@ -219,10 +219,10 @@ public:
             this bundle. As SVG images usually don't have any natural
             default size, it should be provided when creating the bundle.
      */
-    static wxBitmapBundle FromSVG(char* data, const wxSize sizeDef);
+    static wxBitmapBundle FromSVG(char* data, const wxSize& sizeDef);
 
     /// @overload
-    static wxBitmapBundle FromSVG(const char* data, const wxSize sizeDef);
+    static wxBitmapBundle FromSVG(const char* data, const wxSize& sizeDef);
 
     /**
         Check if bitmap bundle is non-empty.
@@ -254,7 +254,7 @@ public:
         this will create many bitmaps that will never be deleted and will
         consume resources until the application termination.
      */
-    wxBitmap GetBitmap(const wxSize size) const;
+    wxBitmap GetBitmap(const wxSize& size) const;
 };
 
 /**
@@ -277,7 +277,7 @@ public:
                 ... determine the minimum/default size for bitmap to use ...
             }
 
-            wxBitmap GetBitmap(const wxSize size) wxOVERRIDE
+            wxBitmap GetBitmap(const wxSize& size) wxOVERRIDE
             {
                 ... get the bitmap of the requested size from somewhere and
                     cache it if necessary, i.e. if getting it is expensive ...
@@ -312,7 +312,7 @@ public:
         Note that this function is non-const because it may generate the bitmap
         on demand and cache it.
      */
-    virtual wxBitmap GetBitmap(const wxSize size) = 0;
+    virtual wxBitmap GetBitmap(const wxSize& size) = 0;
 };
 
 /**