WordPress 3.2 introduced several enhancements to the `copy_dir()` function:
* No more re-installing Akismet upon upgrade.
* Respect custom `WP_CONTENT_DIR` for bundled plugins/theme installation.
* Respect custom `WP_CONTENT_DIR`/`WP_LANG_DIR` for language files when upgrading.
* Add an exclusion list to `copy_dir()` as well as `WP_Filesystem_Base::wp_lang_dir()`.
* Standardize `WP_Filesystem` path method returns.
However, the version of `copy_dir()` that runs during the upgrade process is the one from the older install, not the newer, which means that these enhancements would only be available after upgrading to WordPress 3.2 first, e.g. in a subsequent upgrade to WordPress 3.3.
In order to make these enhancements immediately available in WordPress 3.2, specifically to take advantage of skip lists and avoid re-installing Akismet if it was previously deleted, a temporary copy of the function was utilized, with the intention to remove it in WordPress 3.3 or a later release.
With further enhancements made to the Upgrade API to support partial and no-content builds, this temporary copy is no longer relevant and can be safely removed.
Follow-up to [17576], [17580], [17581], [18225].
Props afragen, costdev, dd32, peterwilsoncc, SergeyBiryukov.
Fixes#55712. See #17173.
Built from https://develop.svn.wordpress.org/trunk@54143
git-svn-id: http://core.svn.wordpress.org/trunk@53702 1a063a9b-81f0-0310-95a4-ce76da25c4cd
4229519bec