Changed behaviour of wxImageResizeQuality parameter in wxImage.Scale and wxImage...

Changed behaviour of wxImageResizeQuality parameter in wxImage.Scale and wxImage.Rescale.

Made the following changes:

* Formerly specifying to resize using wxIMAGE_QUALITY_BICUBIC or wxIMAGE_QUALITY_BILINEAR could result in the ResampleBox method being used. Now always resize with the method that the user actually specified.

* Added wxIMAGE_QUALITY_BOX_AVERAGE to explicitly allow resizing with the ResampleBox method.

* Previously wxIMAGE_QUALITY_HIGH was equal to wxIMAGE_QUALITY_BICUBIC. It has been changed to use wxIMAGE_QUALITY_BOX_AVERAGE when reducing the size of an image and wxIMAGE_QUALITY_BICUBIC in all other cases.

Closes #12845.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67203 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775