Remove unnecessary return by reference

[scribu]

There are several functions in WP that return an object by reference.

With PHP5, this is not necessary anymore.

Examples of such functions: get_post(), get_term().

I don't know how much the trade-off is for that, but the ​PHP manual says the following:

Returning by reference is useful when you want to use a function to find to which variable a reference should be bound. Do not use return-by-reference to increase performance. The engine will automatically optimize this on its own. Only return references when you have a valid technical reason to do so.

I think in PHP 4 code it was returned by reference for memory reasons. We should not do that any longer because we don't need it.

Related: #16661, #16813, #16917

16752.patch​ as an example. This private function did return by reference, but the callee never received as reference. That's fixed.

The patch additionally shows that it's now possible to call object methods on function returns.

better return for get_term

better returns for get_term and get_post

This has been shown to create back-compat problems.

removed for get_post in [21597]