[Mod] Windows Glow: windows textures are much darker than in original game

This mod mostly works fine, but windows are much darker than in Morrowind.

See this forum thread: https://forum.openmw.org/viewtopic.php?f=40&t=3906

OpenMW version: current master (df3b4fe6).

(RM-3833 from redmine: created on 2017-04-19 by Andrei Kortunov, , closed on 2017-08-27 by scrawl .)