Small survey tool enhancement

[Sevenless]

When digging in a survey area, it would be super helpful the the corners that are too steep for you to raise/lower the current spot you're trying to work with would flash briefly when you get the "Too steep to dig here" or "Too steep to place any more dirt" messages. Referring to when you're doing it manually instead of the "make level" button, since nice things like slopes and fancy stuff aren't going to be implemented any time soon for sure.

Eyeballing that is pretty difficult.

[jorb]

Could be nice, yeah, though I'm not sure it's trivial. Will consider.

Edit: (Ah, I'd already made a note to look at that, even)