Logged out warnings:
- Don't use <base> tag to set target="_blank". It can break form submission. Instead, set target only on links with JS.
- Fix same domain comparison in wp_auth_check_html() when FORCE_SSL_LOGIN == true.
- Properly show/hide the "Close" button when the dialog is shown multiple times.
See #23295

git-svn-id: https://core.svn.wordpress.org/trunk@24208 1a063a9b-81f0-0310-95a4-ce76da25c4cd