Fix loading of top to bottom BMP files in wxMSW wxBitmap.

The native LoadImage() function used by wxBMPFileHandler only supports the
standard bottom to top BMPs, fall back to our own implementation in wxImage
wxBMPHandler if it fails to also support the top to bottom ones.

Closes #13650.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76041 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775