Allow an `array()` to be passed as the value for `orderby` to `WP_Query`. Allows for an independent `order` value for each key.

Example: `'orderby' => array( 'title' => 'DESC', 'menu_order' => 'ASC' )`.

Adds docs and unit tests.

Props wonderboymusic, johnbillion, DrewAPicture, dd32, andy.
See #17065.

Built from https://develop.svn.wordpress.org/trunk@29027


git-svn-id: http://core.svn.wordpress.org/trunk@28815 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Use wp_hash() instead of AUTH_KEY in WP_Customize_Widgets::get_instance_hash_key().

props juliobox.
fixes #28783.
Built from https://develop.svn.wordpress.org/trunk@29028


git-svn-id: http://core.svn.wordpress.org/trunk@28816 1a063a9b-81f0-0310-95a4-ce76da25c4cd