Slug generator malfunctions on accent characters

[jeffpaul]

As noted by a WordPress.org support forum post by [@viewup](https://wordpress.org/support/users/viewup/), the slug generator in Customize Posts differs from what the standard WP Admin generates when an accented character is included.

Example: "Catálogos" turns into “cat-logos” in Customize Posts but “catalogos” in WP Admin.

Desired result: Customize Posts slug generator "normalizes" the slug text to the unaccented character to match output from the standard WP Admin.