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.


git-svn-id: https://develop.svn.wordpress.org/trunk@28764 602fd350-edb4-49c9-b593-d223f7449a82
Fix abbreviations mixed with quotes, example: `'99% of people'`.
Add/alter unit tests.

Props miqrogroove.
Fixes #26850.


git-svn-id: https://develop.svn.wordpress.org/trunk@28765 602fd350-edb4-49c9-b593-d223f7449a82