Currently users by default have transparent window frames and doors.
Turns out that at some point there was a switch from RGBT to RGBA, which
means last transparency element differs in the range of transparency
that it specifies (RGBT, where 1 - fully visible, RGBA where 1 - fully
transparent). As the changed happened, all of the windows and door
became transparent.
This patch changes that, from RGBT to RGBA so we will map transparency
properly, as well as adding a possibility to set transparency through
material.
d63382262e