Remove old links_recently_updated_* DB options that never had a UI.

fixes #27649.

Built from https://develop.svn.wordpress.org/trunk@27916


git-svn-id: http://core.svn.wordpress.org/trunk@27746 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Edit Image modal:
- Fix issue with adding a link to an image that didn't have one previously.
- Adjust the look-and-feel of the advance options toggle so that it becomes a section heading that can be open/closed.
- Add a Custom Size option to the size drop-down that reveals fields for soft-resizing the image inserted into the post.
Props gcorne, and props sdasse for the design help, see #27366
Built from https://develop.svn.wordpress.org/trunk@27918


git-svn-id: http://core.svn.wordpress.org/trunk@27748 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE:
- Bring back loading of /langs/[locale].js and /langs/[locale]_dlg.js from PHP. Prevents errors with missing translation files when custom plugins use requireLangPack() without second argument.
- Back to using ISO 639-1 (two letter) locales as the locale is used as part of the translation file name.
See #24067, fixes #27610
Built from https://develop.svn.wordpress.org/trunk@27922


git-svn-id: http://core.svn.wordpress.org/trunk@27752 1a063a9b-81f0-0310-95a4-ce76da25c4cd