Canonical callback representation

[scribu]

Since PHP 5.3, you have various ways of passing the same callback:

add_action( 'the_content', array( 'My_Plugin_Main_Class', 'the_content' ) );

add_action( 'the_content', 'My_Plugin_Main_Class::the_content' );

add_action( 'the_content', '\\My_Plugin_Main_Class::the_content' );

Currently, you have to use the exact same syntax in remove_action(), or it won't work.

It would be nice if _wp_filter_build_unique_id() converted all these variations to a canonical representation.