Add Unit Tests for `get_comment_pages_count()`. Fix a notice caused when `$wp_query->comments` is not set in that function.

Props mdbitz, markjaquith.
Fixes #20633.


Built from https://develop.svn.wordpress.org/trunk@27055


git-svn-id: http://core.svn.wordpress.org/trunk@26928 1a063a9b-81f0-0310-95a4-ce76da25c4cd
In `wpdb::db_connect()`, allow the loading of a custom database error template - this is already allowed in `dead_db()`.

In `dead_db()`, move the call to `wp_load_translations_early()` before the inclusion of the `db-error.php` file to allow translation in both locations before the template is loaded.

Props sbruner, kovshenin.
Fixes #25703.


Built from https://develop.svn.wordpress.org/trunk@27056


git-svn-id: http://core.svn.wordpress.org/trunk@26929 1a063a9b-81f0-0310-95a4-ce76da25c4cd