Add parameter user_only to get_declared_classes(interfaces/traits)

Hi internalers:

     there comes a FR, #62343 https://bugs.php.net/bug.php?id=62343

     the bug self is about class alias,  but it also metioned a new
parameter $user_only to get_declared_classes.

     the FR makes sense to me,  for now,  get_defined_functions 's
return will points which functions are internal, and which is user
defined.

     but get_declared_classes etc doesn't.

     so I made a patch
https://bugs.php.net/patch-display.php?bug_id=62343&patch=bug62343.phpt&revision=latest

     yes, the patch have some room for improving,  like promote the
condition (ce->type == ZEND_USER_CLASS) out of the iterating :)

     for now, I just what to see what do you think about this idea?
:)  (hope I made my point clear)

Why not use something like get_defined_functions()'s return : a double
array of [internal] => array, [user] => array ?
It would just make the get_defined_functions()'s API more consistent IMO.
We could embrace the [ bool $categorize = false ] API from
get_defined_constants() as well , the goal would be to take this bug
as an entry point to standardize those functions' API without BBC

Julien.P