From Jan Peciva, "I am sending four fixes to obj plugin:

- materialName used to be not stripped of whitespace, making number of models
fail to load materials; now fixed
- stripping was considering spaces only, thus models using tabs had problems
to load correctly; fixed
- fixed references to textures; they did not performed conversion to native
directory separators
- make d (dissolve) takes precedence over Tr (transparency); there seems to be
a confusion about the Tr item - some claiming 1 to be opaque and 0
transparent, while number of models uses exactly the opposite. d (dissolve),
if present in the model, does not suffer from this confusion, thus using it
instead fixes the problem for many many models.

I put many comments to the file concerning d and Tr item as others may further
investigate. Let me know in the case of any problems."