Replace EG(autoload_func) with a C level zend_autoload hook.
This avoids having to do one indirection through PHP function
calls. The need for EG(autoload_func) was a leftover from the
__autoload() implementation.
Additionally, drop special-casing of spl_autoload(), and instead
register it just like any other autoloading function. This fixes
bug #71236 as a side-effect.
Finally, change spl_autoload_functions() to always return an array.
The distinction between false and an empty array no longer makes
sense here.
Closes GH-5696.
This is a fix for symfony/symfony#32995.
The behavior is:
* Throwing exception when loading parent/interface is allowed
(and we will also throw one if the class is simply not found).
* If this happens, the bucket key for the class is reset, so
it's possibly to try registering the same class again.
* However, if the class has already been used due to a variance
obligation, the exception is upgraded to a fatal error, as we
cannot safely unregister the class stub anymore.
Máté Kocsis