Allow language specified by the WPLANG constant (but not installed) to be chosen.

fixes #29456.

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Editor scrolling: Avoid jumping to the cursor when modifier and scrolling keys are pressed.

fixes #29485.

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Editor scrolling: Remember and restore scroll position for visual and text modes.

This prevents the editor from jumping off screen when the rendered visual content is significantly taller than plain text, e.g. when there are views present.

This is also a close restoration of 3.9 behavior, some of which was browser-specific.

props avryl.
fixes #29338.

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Language Pack Upgrader: Allow to disable asynchronously translation updates.

* Don't touch VCS installs.
* Use the `async_update_translation` filter (which corresponds exactly to `auto_update_translation`) to entirely disable it, or based on the update offer. 

props nacin, ocean90.
fixes #28571.
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Restore the post type's view_item label for preview links that don't submit the changes.

fixes #28350.
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git-svn-id: http://core.svn.wordpress.org/trunk@29470 1a063a9b-81f0-0310-95a4-ce76da25c4cd
4.0-RC2.

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Modals: Remove yet more cruft that was causing unwanted coloration of icons.

props celloexpressions.
fixes #29147 (for real this time).

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Editor expand: revert back to scrolling to the editor top when switching Visual to Text, fixes #29338
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4.0-RC3.

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Add 'Release Lead' string to credits. see #29494.

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Merge pull request #8 from WordPress/master

Update