Avoid our pre-flight writable checks if get_core_checksums() doesn't exist yet.

Thus, it will not work for 3.6 => 3.7, only 3.7+.

see #22704.

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git-svn-id: http://core.svn.wordpress.org/trunk@25710 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Remove accidental debug cruft in [25780]. see #22704.

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git-svn-id: http://core.svn.wordpress.org/trunk@25711 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Use correct variable. see #22704.

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git-svn-id: http://core.svn.wordpress.org/trunk@25712 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Significantly simplify get_core_checksums(), as the caching and chunking was causing too much grief.

Make sure we only do our pre-flight is_writable check when the file exists.

see #18201. see #22704.

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git-svn-id: http://core.svn.wordpress.org/trunk@25713 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fourteen: better logic for featured image HTML output, and add fallback message for focusable anchor elements, for accessibility. Fixes #25325.
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git-svn-id: http://core.svn.wordpress.org/trunk@25714 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fourteen: link hover improvements, props sabreuse. See #25054.
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git-svn-id: http://core.svn.wordpress.org/trunk@25715 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fourteen: remove excerpts from featured posts, and display full titles instead. Props iamtakashi, closes #25581.
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git-svn-id: http://core.svn.wordpress.org/trunk@25716 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Avoid numerous potential PHP warnings when dealing with the pre-r25801 get_core_checksums() return value.

Warnings included current(), filestat(), and md5_file().

see #18201. see #22704.

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git-svn-id: http://core.svn.wordpress.org/trunk@25717 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Language Packs: Many many fixes such as:
- Add a "Update Translations" stand-alone button to the updates page
- Shift Language feedback to before update process completion action links & limit the verbosity of output (name + success/errors)
- Simplify/combine the language update descriptive string to only include a plugin/theme name
- Properly handle cache clearing after language updates to prevent langs being repeditively updated
- Display a "All items up to date" string when there's nothing to do
- Reduce the 'Connection Information' from a <h2> to a <h3> to remove duplicate h2's and screen icons from update screens
- Fix the Direct filesystem method not being used for Language updates because WP_LANG_DIR doesn't exist (check it's parent for writable instead)
See #18200, #22704


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git-svn-id: http://core.svn.wordpress.org/trunk@25718 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Remove the no longer used Headerless_Upgrader_Skin class, it's been replaced by Language_Pack_Upgrader_Skin.
See #18200, [25806]

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git-svn-id: http://core.svn.wordpress.org/trunk@25719 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fourteen: first pass at implementing Featured Content settings, props obenland. See #25549.
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git-svn-id: http://core.svn.wordpress.org/trunk@25720 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Avoid printing a possible HTML element. fixes #24813.

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git-svn-id: http://core.svn.wordpress.org/trunk@25721 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Include translations in the update bubbles (as +1 if there are any). see #18200.

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git-svn-id: http://core.svn.wordpress.org/trunk@25722 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Avoid a few PHP Warnings when files don't exist and use a better method to locate the local filepath.
See #18201

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git-svn-id: http://core.svn.wordpress.org/trunk@25723 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix a issue where the translation name isn't showing up in the Background Update emails, caused by a PHP Warning/missing variable in [25806]. See #18200

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git-svn-id: http://core.svn.wordpress.org/trunk@25724 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fourteen: implement tag auto-complete for featured content settings, and uppercase `__CLASS__` for consistency. Props kovshenin, see #25549.
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git-svn-id: http://core.svn.wordpress.org/trunk@25725 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fourteen: cleanup, props iamtakashi. Fixes #25613.

 * With the ephemera widget in place, `content-recent-formatted-post.php` is unused, see #25028.
* We're no longe filtering formatted posts from the main query, see #25330.
 * Fix a typo.
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git-svn-id: http://core.svn.wordpress.org/trunk@25726 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Merge the should_auto_update() and can_auto_update() methods. see #22704.

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git-svn-id: http://core.svn.wordpress.org/trunk@25727 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Update the banner for update-core.php that tells users they are set up for security updates to happen in the background.

"This site is set up to install security updates of WordPress automatically. Cool!"

Checkmark is a placeholder; we'll tinker with this further today.

see #22704.

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git-svn-id: http://core.svn.wordpress.org/trunk@25728 1a063a9b-81f0-0310-95a4-ce76da25c4cd
When a plugin enables Background Plugin	updates, don't deactivate the plugin during update as we require a browser to reactivate it afterwards. See #22704

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git-svn-id: http://core.svn.wordpress.org/trunk@25729 1a063a9b-81f0-0310-95a4-ce76da25c4cd