Use high quality in wxBitmap::Rescale()

This function is currently used for relatively small icons in
wxArtProvider and wxSearchCtrl, so it shouldn't be a problem to use
wxIMAGE_QUALITY_HIGH from performance point of view and if it ever does
become a problem, the application could easily use wxImage::Rescale()
with a different option directly instead.

src/common/bmpbase.cpp

@@ -71,7 +71,7 @@ void wxBitmapHelpers::Rescale(wxBitmap& bmp, const wxSize& sizeNeeded)
 
 #if wxUSE_IMAGE
     wxImage img = bmp.ConvertToImage();
-    img.Rescale(sizeNeeded.x, sizeNeeded.y);
+    img.Rescale(sizeNeeded.x, sizeNeeded.y, wxIMAGE_QUALITY_HIGH);
     bmp = wxBitmap(img);
 #else // !wxUSE_IMAGE
     // Fallback method of scaling the bitmap