Holes aren't plotted #65
Description
The following operations create a shape with a hole in it. The hole is there but is not displayed in the plot. The same thing happens with any other operations that create a hole. This confused me for ages because I thought shapes with holes weren't supported at all and I was trying to work around that, so it would definitely be better if holes were plotted properly.
shape = readgeom("LINESTRING(0 0, 0 2, 1 1, 2 2, 2 0, 0 0)")
shape = buffer(shape, 0.25, 3)
plot(shape)
## uncomment these lines to 'fake' plotting the hole
#inner = LibGEOS.Polygon([coordinates(shape)[2]])
#plot!(inner,color="white")plot without the hole:
plot with a 'fake' hole showing roughly how it should look:
