#1 Fix for textures in u3d files

[Henrik Carlqvist]

I first sent this patch to the meshlab patch tracker, but now after having read some in the meshlab svn repository I realize that the patch might belong to this project.

When converting a 3ds file to a u3d file with textures
using the following command:

meshlabserver -i file.3ds -o file.u3d -om wt

IDTFConverter bails out as the generated idtf file is broken. I was
using meshlab 1.3.0a.

The attached patch fixes this problem and makes it possible to convert files to u3d format with textures.

[Henrik Carlqvist]