Support palettized DDS files

Mounrhold Ash Trees by Wollibeebee is rendered in pink.

Attached Save, Pic, Log and the Mod.

The log says: Error loading textures\vurt_wl_cherryb03.dds: code 1 Error loading textures\vurt_wl_cherryb05.dds: code 1 Error loading textures\vurt_wl_goldenbark.dds: code 1

0.40.0+git201612151916~ubuntu16.04.1 Linux Mint 18 64 bits.

(RM-3668 from redmine: created on 2016-12-16 by Amenophis ., )

Attachments: openmw.log Flora_-Tribunal-Wollibeebee-_Mounrhold_Ash_Trees-42453-.7z Wollie_ash_trees_rendering_bug.7z