weighted normals as the render engine, and the render engine will copy
normals from the mesh rather than always recalculating them.
Subsurf/multires still use regular vertex normals, but they are expected
to be sufficiently high resolution to not need this.
This means that normal maps displayed in the viewport actually match the
render engine exactly and don't have artifacts due to this discrepancy.
It of course also avoids unexpected surprises where your render normals
look different than your viewport normals.
Subversion bumped to 4 for version patch to recalculate normals.
Patch by Morten Mikkelsen, with some small changes.
549b5e1222