libmediainfo: 17.10 -> 17.12

Semi-automatic update. These checks were performed:

- built on NixOS
- found 17.12 with grep in /nix/store/8x38418jc8j511k8dk4jc2if6iizbz2b-libmediainfo-17.12
- found 17.12 in filename of file in /nix/store/8x38418jc8j511k8dk4jc2if6iizbz2b-libmediainfo-17.12

cc "@devhell"