securefs: 0.3.2 -> 0.8.1

Semi-automatic update. These checks were performed:

- built on NixOS
- ran `/nix/store/r1icgafqy02cz35kjkxr86hxj8mj1nyv-securefs-0.8.1/bin/securefs version` and found version 0.8.1
- found 0.8.1 with grep in /nix/store/r1icgafqy02cz35kjkxr86hxj8mj1nyv-securefs-0.8.1
- found 0.8.1 in filename of file in /nix/store/r1icgafqy02cz35kjkxr86hxj8mj1nyv-securefs-0.8.1