Prevent stomping $wp_the_query by accident

[scribu]

We have this in wp-settings.php:

$wp_query =& $wp_the_query;

This was necessary in PHP4, but in PHP5 it makes it easy to overwrite $wp_the_query by accident:

// tra la la, some template file

$wp_query = new WP_Query( ... );

and in general it obscures the fact that $wp_the_query should remain frozen.

[wpmuguru]

Attached is a page template for 2012 that demonstrates that wp_reset_query does not reset to the original query when the global $wp_query is assigned a new WP_Query. This problem is fixed by 22125.diff.

The bug was introduced in [21792]. Prior to that change query_posts returned a reference which replaced the existing $wp_query reference. After the change query_posts is returning an object which replaces the referenced object.

[ryan]

In 22434:

Don't assign wp_the_query to wp_query by reference. Removing the ref avoids accidentally stomping wp_the_query.

Props scribu, wpmuguru
fixes #22125