Avoid 'Only variables should be passed by reference' warning. fixes #23232.
Pass old roles to set_user_role action. props awellis13. fixes #19134.
Cast post_author to string in XML-RPC methods. props markoheijnen. fixes #22324.
Display username (user_login) rather than user_nicename in Toolbar. fixes #22121.
Use digraphs for German umlauts in remove_accents(). props SergeyBiryukov, ocean90. fixes #3782.