2.5 inflector

Correct and complete transliterations for `Inflector::slug()`.

Some important ones have been missing, e.g. the German `'/ẞ/' => 'SS'`.
Also ordered it alphabetically for better overview.

It does not remove any, only adds missing ones. So it should be - at least regarding to tests - be 100% BC. But to be safe I did not make it against master, but 2.5.