Post formats compat output:

* Check for theme support of `structured-post-formats` rather than `post-formats`.
* Use \n instead of PHP_EOL constant.
* Add new lines after opening compat wrapper tag for some `wpautop()` treatment.

props SergeyBiryukov. see #23347.


git-svn-id: https://core.svn.wordpress.org/trunk@23468 1a063a9b-81f0-0310-95a4-ce76da25c4cd