non-orthogonal 4 cornered building

[maning]

Not sure how to implement this, basic idea is:

1. Get all buildings that only has 4 corners.
2. Get bearing for each line.
3. For each connected lines, compute the interior angle.
4. Get all buildings whose corners are not equal to 90 degrees.

JOSM validator or any other Q/A tool that I know of has this feature.

@rub21 @geohacker @planemad

[maning]

There will edge cases like diamond shaped buildings, but I suspect there are very few.