Polylang Pro 3.6.4

* Minimum WordPress version is now 4.9
* Pro: Strings translations can now be exported and imported (in PO format)
* Pro: Allow to decide individually which ACF fields to copy or synchronize
* Pro: Add action pll_inactive_language_requested
* Pro; Fix fatal error in The Events Calendar compatibility when no language is defined yet
* Pro: Fix bulk translate when a post has no language
* Pro: Fix reusable block saved without language
* Pro: Fix post requested by slug not filtered in REST API, when the slug is shared
* Add a setup wizard
* Add Swahili, Upper Sorbian, Sindhi and Spanish from Uruguay to the list of predefined languages
* Add flags in the predefined list of languages
* Allow to hide the metaboxes from the screen options
* The deletion of the plugin's data at uninstall is now controlled by a PHP constant instead of an option #456
* Add parent in ajax response when selecting a term in autocomplete field #328
* Add Vary: Accept-Language http header in home page redirect. Props @chesio #452
* Improve performance to register/unregister WPML strings
* Add support for the action wpml_switch_language
* Add post_status to the list of accepted args of pll_count_posts()
* Apply the filter pll_preferred_language in wp-login.php
* Use filtered wrappers to create meta when creating media translations #231
* Allow to translate the Twenty Seventeen header video Youtube url #460
* Notices are now dismissed per site instead of per user #478
* Fix terms not visible in the quick edit when only one language is defined and teh admin language filter is active
* Fix post state not displayed for translations of the privacy policy page #395
* Fix wildcards not correctly interpreted in wpml-config.xml
* Fix product categories with special characters duplicated when importing WooCommerce products #474

* Pro: Fix sticky posts not filtered in REST API (introduced in 2.6.9)
* Fix wrong language detected if a child page uses the slug of another language
* Fix a PHP notice with PHP 7.4. #438
* Fix lang-item-first class in language switcher when the current language is hidden. #445
* Fix partially a conflict with Fusion Builder (the other part of the conflict being in Fusion Builder).

* Pro: Use 'parse_query' rather than 'rest_{$type}_query' to filter REST requests.
* Pro: Filter the comments REST endpoint.
* Pro: Fix duplication of terms without language.
* Pro: Fix fatal error when Admin Columns is activated and no language is defined yet.
* Fix shortlink when using one subdomain or domain per language