Allow `the_title_attribute()` to receive a `post` argument, and use this in `get_adjacent_post_rel_link()` to make sure tags are stripped from the title output there.

Fixes #24232.

git-svn-id: http://core.svn.wordpress.org/trunk@24783 1a063a9b-81f0-0310-95a4-ce76da25c4cd