CHUNK_ID_XYZI voxel bounds check to improve handling of corrupt files

[dougbinks]

I've encountered a number of vox files which were corrupt with voxels outside the bounds of the model size. This results in the voxel array bounds being overwritten when loaded.

There's already an assert in the code, but this PR adds the same test to adding the voxel data to the array. I've been able to recover some data from models which otherwise would not load with this addition and I don't think the performance hit is significant.

[mgerhardy]

This is also part of #58 - with ogt_warn

[dougbinks]

Ah, I didn't spot that. This can be closed if you're intending to accept that change.

[mgerhardy]

Well, I would be thankful on your input on where I've added the ogt_warn stuff and where it still is ogt_assert. Not sure if my PR would get accepted that way. Let's see

[dougbinks]

I'll take a look soon.