Forward pingback IP during pingback verification.

props tellyworth, nacin.
fixes #27613.


git-svn-id: https://develop.svn.wordpress.org/trunk@27872 602fd350-edb4-49c9-b593-d223f7449a82
Clarify inline documentation for the 'html5' case and PHPDoc return in `add_theme_support()`.

Props jond3r.
Fixes #27278.


git-svn-id: https://develop.svn.wordpress.org/trunk@27879 602fd350-edb4-49c9-b593-d223f7449a82
Clarify PHPDoc return description for `media_handle_upload()`.

Props jdgrimes.
Fixes #27519.


git-svn-id: https://develop.svn.wordpress.org/trunk@27880 602fd350-edb4-49c9-b593-d223f7449a82
Revert [27654] for strings.

props westonruter.
fixes #27485.

git-svn-id: https://develop.svn.wordpress.org/trunk@27890 602fd350-edb4-49c9-b593-d223f7449a82
Widget Customizer: Remove WidgetCustomizer.showFirstSidebarIfRequested().

It's currently unused and needs another iteration.

see #27290.

git-svn-id: https://develop.svn.wordpress.org/trunk@27891 602fd350-edb4-49c9-b593-d223f7449a82
Merge branch 'master' into a11y