Show deprecation notices

[deshack]

We do not have the needed file right now, so I'll put it here until we have something to place this into.
This hook should be run just before outputting content. Running it before could bring to some deprecation notices not being showed.

We could also consider running this same hook after the content, in case some view files are deprecated.

The hook should be something like:

$hook->add( 'deprecated_exception', function() {
    $hook->run( 'deprecated_function_exception' );
    $hook->run( 'deprecated_file_exception' );
    $hook->run( 'deprecated_argument_exception' );
} );
$hook->run( 'deprecated_exception' );