Support 'EXISTS' and 'NOT EXISTS' in `WP_Tax_Query`.

These new values for the 'operator' parameter make it possible to filter items
that have no term from a given taxonomy, or any term from a given taxonomy.

Includes unit tests.

Fixes #29181.
Built from https://develop.svn.wordpress.org/trunk@29896


git-svn-id: http://core.svn.wordpress.org/trunk@29651 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: clean up skip-link-focus-fix.js, see #29799
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git-svn-id: http://core.svn.wordpress.org/trunk@29652 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Admin menu:
- Fix pinning after resizing the window.
- Merge the two DOM ready callbacks in common.js
- Fix the submenus position adjustment on focus.
See #29806
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git-svn-id: http://core.svn.wordpress.org/trunk@29653 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add line breaks at the end of network setup rules to avoid unintended merging with a subsequent line.

props socki03.
fixes #29945.
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git-svn-id: http://core.svn.wordpress.org/trunk@29654 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: Update some more bundled theme references after [29895].

see #29799.
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git-svn-id: http://core.svn.wordpress.org/trunk@29655 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Support nested tax query syntax in redirect_canonical().

The proper place to look for a list of queried terms is in the flat
queried_terms array, not in tax_query->queries.

See #29738.
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git-svn-id: http://core.svn.wordpress.org/trunk@29656 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Avoid redundant table joins in WP_Tax_Query.

IN clauses that are connected by OR require only a single table join. To avoid
extraneous joins, keep track of generated table aliases, and let sibling
clauses piggy-back on those aliases when possible.

Introduces WP_Tax_Query::sanitize_relation() to reduce some repeated code.

Adds unit tests to verify the JOIN consolidation, and integration tests for
cases where JOINS are being combined.

Props boonebgorges, otto42, jakub.tyrcha.
Fixes #18105.
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git-svn-id: http://core.svn.wordpress.org/trunk@29657 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Customizer: Change instances of "Theme Customizer" to just "Customizer", as the Customizer isn't necessarily theme-specific.

Also capitalize "Customizer".
See also https://make.wordpress.org/core/2014/07/08/customizer-improvements-in-4-0/.

props studionashvegas, tareq1988.
fixes #29947.
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git-svn-id: http://core.svn.wordpress.org/trunk@29658 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Theme install: Remove unused strings.

fixes #29488.
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git-svn-id: http://core.svn.wordpress.org/trunk@29659 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Customizer: Only POST dirty settings to preview to improve performance.

props westonruter.
fixes #29983.
Built from https://develop.svn.wordpress.org/trunk@29905


git-svn-id: http://core.svn.wordpress.org/trunk@29660 1a063a9b-81f0-0310-95a4-ce76da25c4cd