Update help content for Dashboard. props kpdesign. fixes #26632.
Built from https://develop.svn.wordpress.org/trunk@27043


git-svn-id: http://core.svn.wordpress.org/trunk@26917 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE: add dashicon for the "wp_page" button, see #24067.
Built from https://develop.svn.wordpress.org/trunk@27044


git-svn-id: http://core.svn.wordpress.org/trunk@26918 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add wp_install and wp_upgrade hooks to the respective functions.

props Denis-de-Bernardy.
fixes #25762.

Built from https://develop.svn.wordpress.org/trunk@27045


git-svn-id: http://core.svn.wordpress.org/trunk@26919 1a063a9b-81f0-0310-95a4-ce76da25c4cd