Yank version numbers out of translated strings. TODO decide whether this...

Yank version numbers out of translated strings. TODO decide whether this should be major version only, which probably means about.php should also contain text about x.y vs x.y.z. see #18742.

git-svn-id: https://core.svn.wordpress.org/trunk@19140 1a063a9b-81f0-0310-95a4-ce76da25c4cd