Part I of inline documenation for hooks in wp-includes/post.php.

Adds docs for the following hooks:
* `get_attached_file`
* `update_attached_file`
* `_wp_relative_upload_path`
* `post_type_labels_{$post_type}`
* `edit_{$field}`
* `{$field_no_prefix}_edit_pre`
* `edit_post_{$field}`
* `pre_{$field}`
* `{$field_no_prefix}_save_pre`
* `pre_post_{$field}`
* `{$field}_pre`
* `$field`
* `post_{$field}`
* `wp_count_posts`
* `wp_count_attachments`
* `post_mime_types`
* `wp_insert_post_empty_content`

See #25376.

Built from https://develop.svn.wordpress.org/trunk@28041


git-svn-id: http://core.svn.wordpress.org/trunk@27871 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Clarify documentation for hooks in `sanitize_post_field()`.

* `edit_post_{$field}` pairs with `edit_{$field}`
* `pre_post_{$field}` pairs with `pre_{$field}`
* `post_{$field}` pairs with `{$field}`

As the above pairs' docs are unnecessarily duplicative, the second sets of docs have been removed. Also, the "duplicates" are purposely not marked as such in this case as the hook names differ. Also remove `@deprecated` tags mistakenly left in in [28041].

See #25376.

Built from https://develop.svn.wordpress.org/trunk@28042


git-svn-id: http://core.svn.wordpress.org/trunk@27872 1a063a9b-81f0-0310-95a4-ce76da25c4cd
DFW:
- Move the word count and "Just Write" to a fixed bar at the bottom.
- Fix responsive mode to 480px. Narrower screens will have a scroll bar.
- Hide the Help button on screens < 480px, move the Save button to the right, make it bigger to match the others, and other responsive mode fixes.
Fixes #26907, see #27709
Built from https://develop.svn.wordpress.org/trunk@28043


git-svn-id: http://core.svn.wordpress.org/trunk@27873 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Widget Customizer: Fix widget filtering.

props westonruter.
fixes #27451.
Built from https://develop.svn.wordpress.org/trunk@28044


git-svn-id: http://core.svn.wordpress.org/trunk@27874 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Precommit cleanup for theme.js, editor.css amd wpdialogs/plugin.js, See #27055, #26907, #16284
Built from https://develop.svn.wordpress.org/trunk@28045


git-svn-id: http://core.svn.wordpress.org/trunk@27875 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Move `toolbar` declaration after the `:visible` check, like it was before [28019].

props kovshenin.
fixes #24859.
Built from https://develop.svn.wordpress.org/trunk@28046


git-svn-id: http://core.svn.wordpress.org/trunk@27876 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Theme Installer: Prevent default events for "Upload Theme" and "Browse" buttons.

see #27055.
Built from https://develop.svn.wordpress.org/trunk@28047


git-svn-id: http://core.svn.wordpress.org/trunk@27877 1a063a9b-81f0-0310-95a4-ce76da25c4cd