TinyMCE: remove strings that are not translated before outputting the translations. Fixes #27797.
Built from https://develop.svn.wordpress.org/trunk@30294


git-svn-id: http://core.svn.wordpress.org/trunk@30293 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix PHP notice in `Tests_Feed_RSS2::test_items()`.

A notice was being thrown when `get_the_tags()` returned false, and `foreach()`
was run over that return value.

See [30283].
Built from https://develop.svn.wordpress.org/trunk@30295


git-svn-id: http://core.svn.wordpress.org/trunk@30294 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE: enable direct calls to `_WP_Editors::wp_mce_translation()`. When using TinyMCE directly, this makes it easier to load the translation of the default strings. Fixes #30293.
Built from https://develop.svn.wordpress.org/trunk@30296


git-svn-id: http://core.svn.wordpress.org/trunk@30295 1a063a9b-81f0-0310-95a4-ce76da25c4cd
`wpdb::flush()` was not flushing results correctly when using mysqli.

This change also allows stored procedures or queries made with `mysqli_multi_query()` to be flushed.

Includes unit tests.

Fixes #28155.

Props soulseekah.

Built from https://develop.svn.wordpress.org/trunk@30297


git-svn-id: http://core.svn.wordpress.org/trunk@30296 1a063a9b-81f0-0310-95a4-ce76da25c4cd