RFC Tracker

Adds a fatal_error_backtraces INI setting, on by default, so fatal errors include a stack trace like exceptions do.

Lets you put attributes, including #[\Deprecated], on constants declared with const, and read them with ReflectionConstant::getAttributes().

Adds curl_share_init_persistent(), which returns a locked persistent curl share handle, reused per option set, that can't share cookies.

Lets static closures appear in constant expressions, such as attribute arguments, parameter and property defaults, and constants.

Makes the Directory class final, blocks new Directory(), cloning, serialization and dynamic properties, so it acts like a resource object.