Clarify inline documentation for the 'html5' case and PHPDoc return in `add_theme_support()`.

Props jond3r.
Fixes #27278.

Built from https://develop.svn.wordpress.org/trunk@27879


git-svn-id: http://core.svn.wordpress.org/trunk@27710 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Clarify PHPDoc return description for `media_handle_upload()`.

Props jdgrimes.
Fixes #27519.

Built from https://develop.svn.wordpress.org/trunk@27880


git-svn-id: http://core.svn.wordpress.org/trunk@27711 1a063a9b-81f0-0310-95a4-ce76da25c4cd