Themes: Search the description too.

props dd32.
fixes #26309.

git-svn-id: https://develop.svn.wordpress.org/trunk@26480 602fd350-edb4-49c9-b593-d223f7449a82
Themes: Add type="search" to search. fixes #26331.

git-svn-id: https://develop.svn.wordpress.org/trunk@26481 602fd350-edb4-49c9-b593-d223f7449a82