Add hook to allow modification of SimplePie options

[nacin]

I suggest an action is added to to the function fetch_feed() in wp-includes/feed.php. This would allow someone to add options to a SimplePie fetch without unnecessarily duplicating the function.

I also don't see a harm in allowing for different cache durations depending on the url. I would find that to be important context. So, I've also added the url as an argument to the wp_feed_cache_transient_lifetime filter.

Patch attached.

Should probably use do_action_ref_array() instead of do_action().

Replying to scribu:

Should probably use do_action_ref_array() instead of do_action().

Good call, not sure how I missed that. Will patch up as array(&$feed, &$url).

Using do_action_ref_array

$url shouldn't be by reference.

Trivial patch, could be committed. Not unlike #11237 from today.

(In [12484]) Pass the url to the 'wp_feed_cache_transient_lifetime' filter to give more context.
Allow plugins to set extra options on SimplePie using the new 'wp_feed_options' action.
Fixes #11117 props nacin.