In `wptexturize()`, adjust for the treatment of abbreviated years at the end of quotations.
Silence some unit tests that have never passed and may no longer be applicable.

Props miqrogroove.
Fixes #18549.

Built from https://develop.svn.wordpress.org/trunk@28764


git-svn-id: http://core.svn.wordpress.org/trunk@28577 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix abbreviations mixed with quotes, example: `'99% of people'`.
Add/alter unit tests.

Props miqrogroove.
Fixes #26850.

Built from https://develop.svn.wordpress.org/trunk@28765


git-svn-id: http://core.svn.wordpress.org/trunk@28578 1a063a9b-81f0-0310-95a4-ce76da25c4cd