Don't split shared terms on term update.

Splitting shared terms means assigning a new term_id to a given term_taxonomy_id.
It was uncovered that this change could cause problems for sites that have
cached the original term_id somehow - say, in postmeta - since future lookups
using that term_id will now fail.

Removing for 4.1-beta1. We'll look at improvements to backward compatibility
to try to get this back into a later beta.

Props mboynes.
See #30335.
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git-svn-id: http://core.svn.wordpress.org/trunk@30335 1a063a9b-81f0-0310-95a4-ce76da25c4cd
When asserting microtime output as a number, make it a number

microtime is by default a string. Doing a greater then or less than check of that string is a bad idea since it uses the first part (the micro part of microtime) rather then the actual time. This adds a helper to convert microtime output into a float which we can then use to properly compare the output of microtime.

This fixes an intermittent test failure.

fixes #30336


Built from https://develop.svn.wordpress.org/trunk@30337


git-svn-id: http://core.svn.wordpress.org/trunk@30336 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Introduce Distraction-Free Writing v2, a re-think of DFW that uses the main editor instance

* the "DFW" button is now an auto/off toggle
* defaulting to auto during beta, decide later for release
* "auto" means that DFW gets enabled as you start typing in editor
* tabbing and mousing out will bring the full interface back
* there is a slight grace period during which your mouse can quickly return

Feature plugin work happened here: https://github.com/avryl/focus

props avryl, azaozz, Michael Arestad
fixes #29806
Built from https://develop.svn.wordpress.org/trunk@30338


git-svn-id: http://core.svn.wordpress.org/trunk@30337 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE: set the image toolbar's z-index higher than the editor when the new DFW is active. See #30147.
Built from https://develop.svn.wordpress.org/trunk@30339


git-svn-id: http://core.svn.wordpress.org/trunk@30338 1a063a9b-81f0-0310-95a4-ce76da25c4cd