Cache 'dynamic' Javascript

[mdawaffe]

The PHP generated Javascript files are not being cached properly.

Attached:

1. Call wp-config.php instead of admin.php to avoid cache blocking and unnecessary overhead.
2. Send Cache-control: max-age=2600000, must-revalidate

These scripts only need the PHP for i18n (if that), so the ~1 month long freshness period shouldn't hurt.

require_once('../wp-config.php');
header('Content-type: text/javascript; charset=' . get_settings('blog_charset'), true);
header('Cache-control: max-age=2600000, must-revalidate', true);  // ~1 month

I see those three lines listed three times, and there will probably be other times as we add more JS functionality in the future. Wanna move that to an include so that there's one place to go to edit it all?

Well if you'd like to be clever about it, sure :)

2799b.diff

1. wp-includes/js/js-headers.php gets the include right and sends the headers.

(In [4109]) cache_javascript_headers() from masquerade. fixes #3059 #2799