ș and ț characters not converted in remove_accents()

[scribu]

ș and ț, which are the correct diacritic marks in Romanian, are not converted by the remove_accents() function, which leads to ugly slugs.

This patch fixes that.

[ryan]

Note that we can't change the sanitizer at all until we have a means of handling slugs made with older versions of the sanitizer. Right now, sanitizer changes will cause old slugs to 404.

[scribu]

But aren't slugs only created once and then stored and retrieved from the db?

[ryan]

Incoming slugs (from permalink requests) are run through the sanitizer and they won't match the old slug.

[Denis-de-Bernardy]

See #9591

[scribu]

ground work