I'm just about to try out the latest STLPort release and I went to apply my 'STLPort 5.0 multiple side by side dlls changes' from 2005 and noticed that the place where one of the changes needs to be made has changed.
The change to Makefile.inc should still be made to STLport-5.1.3\build\lib\Makefile.inc but the change that was previously made to stl_msvc.h now has to be made to STLport-5.1.3\stlport\stl\config\_auto_link.h