libspatialindex: 1.8.1 -> 1.8.5

Semi-automatic update. These checks were performed:

- built on NixOS
- found 1.8.5 with grep in /nix/store/37qfplsqfz7lq058pg2cvvm592yzvvf9-libspatialindex-1.8.5
- found 1.8.5 in filename of file in /nix/store/37qfplsqfz7lq058pg2cvvm592yzvvf9-libspatialindex-1.8.5