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.

src/common/bmpbndl.cpp

@@ -63,7 +63,7 @@ public:
     }
 
     virtual wxSize GetDefaultSize() const wxOVERRIDE;
-    virtual wxBitmap GetBitmap(const wxSize size) wxOVERRIDE;
+    virtual wxBitmap GetBitmap(const wxSize& size) wxOVERRIDE;
 
 #ifdef __WXOSX__
     virtual WXImage OSXGetImage() const wxOVERRIDE;
@@ -156,7 +156,7 @@ wxSize wxBitmapBundleImplSet::GetDefaultSize() const
     return m_entries[0].bitmap.GetSize();
 }
 
-wxBitmap wxBitmapBundleImplSet::GetBitmap(const wxSize size)
+wxBitmap wxBitmapBundleImplSet::GetBitmap(const wxSize& size)
 {
     // We use linear search instead if binary one because it's simpler and the
     // vector size is small enough (< 10) for it not to matter in practice.
@@ -320,7 +320,7 @@ wxSize wxBitmapBundle::GetDefaultSize() const
     return m_impl->GetDefaultSize();
 }
 
-wxBitmap wxBitmapBundle::GetBitmap(const wxSize size) const
+wxBitmap wxBitmapBundle::GetBitmap(const wxSize& size) const
 {
     if ( !m_impl )
         return wxBitmap();