1.18: Update bindings to 1.18

It seems that the 1.18.0 release of gst-sharp doesn't actually contain updated bindings. I've ran the update command with the fixed bindinate and how it generates more symbols, the current bindinate seems to generate some of the code using the installed version of following the GI_TYPELIB_PATH

This was build using https://github.com/GLibSharp/bindinator/pull/2

@tpm You probably want the command from the README.me here to your release script to make sure the bindings are correctly updated.