Explicitly assign menu term relationship rather than piggybacking on wp_insert_post() with the tax_input argument.

That argument currently depends on user context (see #19373).

Adds unit test for properly updating orphaned menu items.

props danielbachhuber.
fixes #27113.

Built from https://develop.svn.wordpress.org/trunk@27556


git-svn-id: http://core.svn.wordpress.org/trunk@27399 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Send a charset header when erroring out in wp_check_php_mysql_versions().

props rodrigosprimo.
fixes #26536.

Built from https://develop.svn.wordpress.org/trunk@27557


git-svn-id: http://core.svn.wordpress.org/trunk@27400 1a063a9b-81f0-0310-95a4-ce76da25c4cd