Add boolean return values to require_if_theme_supports().

props jeffsebring, DrewAPicture.
fixes #26716.
Built from https://develop.svn.wordpress.org/trunk@27217


git-svn-id: http://core.svn.wordpress.org/trunk@27074 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Prevent "Add" button in Tags meta box from wrapping to a new line in ru_RU.

fixes #26510.
Built from https://develop.svn.wordpress.org/trunk@27218


git-svn-id: http://core.svn.wordpress.org/trunk@27075 1a063a9b-81f0-0310-95a4-ce76da25c4cd