Have a way to make transparent airlocks/glass/etc opaque

[rulib]

The transparent airlocks that we see a lot of now, the 1-tile ones, not the immortal sliding doors, should be able to be painted or corroded so that they are opaque, either etching the glass with fluorosulfuric acid or painting it with a bucket of paint. That way you can get some much-needed privacy for murdering. Maybe the ability to paint glass opaque too - this could be a new chem even for this stuff.