Clean up deprecated format_to_post() docs. see #27700.


git-svn-id: https://develop.svn.wordpress.org/trunk@28021 602fd350-edb4-49c9-b593-d223f7449a82
Rename USE_EXT_MYSQL to WP_USE_EXT_MYSQL. see #21663.


git-svn-id: https://develop.svn.wordpress.org/trunk@28022 602fd350-edb4-49c9-b593-d223f7449a82
Make playlist tracks keyboard-accessible. 

Fixes #27644.



git-svn-id: https://develop.svn.wordpress.org/trunk@28023 602fd350-edb4-49c9-b593-d223f7449a82