Properly invalidate the cache for `wp_count_posts()` on insert, trash, or when transitioning `post_status` inside of `_transition_post_status()`. Introduces `_count_posts_cache_key()`. Adds unit tests.

Props mark8barnes, for bringing this to our attention in an initial patch.
Fixes #21879.


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Add braces around conditionals. props TobiasBg. fixes #25704.
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TinyMCE: don't replace <i> with <em> and <b> with <strong> and don't remove them when empty, see #24067, see #23037.
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git-svn-id: http://core.svn.wordpress.org/trunk@26956 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add back missing var definition in wplink.js, props TobiasBg, see #24067
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Minor cleanup (jshint) of wp-fullscreen.js and /wordpress/plugin.js, see #24067
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