Fix labels on installation screen.

props avryl.
fixes #28548.
Built from https://develop.svn.wordpress.org/trunk@28759


git-svn-id: http://core.svn.wordpress.org/trunk@28572 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Prevent get_post_class() and get_body_class() from returning duplicate classes.

props Compute.
fixes #28541.
Built from https://develop.svn.wordpress.org/trunk@28760


git-svn-id: http://core.svn.wordpress.org/trunk@28573 1a063a9b-81f0-0310-95a4-ce76da25c4cd
`wptexturize()` adjustments:
* Only place an apostrophe before a number when it has exactly two digits.
* Never match '99' with the single prime pattern.
* Always assume '99' is an abbreviated year at the end of a quotation.
* Add unit tests.
* Resolves the unit test broken in [28721] for #8775.

See #26850.

Built from https://develop.svn.wordpress.org/trunk@28761


git-svn-id: http://core.svn.wordpress.org/trunk@28574 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add Unit Tests for i18n and `wptexturize()`. Don't confuse closing single quotes and apostrophes.

See #27426.

Built from https://develop.svn.wordpress.org/trunk@28762


git-svn-id: http://core.svn.wordpress.org/trunk@28575 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add unit tests to confirm that `---` is properly converted to `&#8212;` by `wptexturize()` where appropriate.

Props miqrogroove.
Fixes #28483.

Built from https://develop.svn.wordpress.org/trunk@28763


git-svn-id: http://core.svn.wordpress.org/trunk@28576 1a063a9b-81f0-0310-95a4-ce76da25c4cd