Support multiple 'status' values in `WP_Comment_Query`.

This change required turning the SQL concatenation into the generation of an
array, for greater flexibility.

Props karpstrucking, ebinnion.
Fixes #29612.
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Improve global variable setting in `setup_postdata()`.

`setup_postdata()` is responsible for setting a number of global variables
that are used for post pagination (`$pages`, `$page`, `$nextpage`) and the
generation of post excerpts (`$more`). These variables should be sensitive to
the currently running instance of `WP_Query` - rather than the main query -
so that these features work properly inside of secondary `WP_Query` loops.

This changeset moves the logic of `setup_postdata()` into a method on `WP_Query`,
and converts `setup_postdata()` to a wrapper.

Props boonebgorges, wonderboymusic.
See #25349.
Fixes #9256, #20904.
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git-svn-id: http://core.svn.wordpress.org/trunk@30085 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Be more specific in documentation of 'slug' param for `get_terms()`.

Props jfarthing84.
Fixes #23636.
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git-svn-id: http://core.svn.wordpress.org/trunk@30086 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Correct some logic to populate the `defaultValue` variable when `data.defaultValue` begins with a hash symbol.

Props antpb
Fixes #30125

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git-svn-id: http://core.svn.wordpress.org/trunk@30087 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Introduce `'pre_delete_term'` hook.

Props cmmarslender.
Fixes #30127.
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git-svn-id: http://core.svn.wordpress.org/trunk@30088 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Increase both mystery and humanism
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