Context for the signup_hidden_fields hooks.

props jeremyfelt, Cimmo.
fixes #19451.

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Introduce a reset_postdata() method on the WP_Query object, which wp_reset_postdata() now wraps.

props ericlewis.
fixes #24785.

Built from https://develop.svn.wordpress.org/trunk@25601


git-svn-id: http://core.svn.wordpress.org/trunk@25518 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add classes to menus to indicate that an item has sub-items: `.menu-item-has-children` for `wp_nav_menu()` and `.page_item_has_children` for `wp_page_menu()`. props hotchkissconsulting. fixes #23834.

Built from https://develop.svn.wordpress.org/trunk@25602


git-svn-id: http://core.svn.wordpress.org/trunk@25519 1a063a9b-81f0-0310-95a4-ce76da25c4cd