As it is now, `IntlTimeZone`, `IntlCalendar` and `IntlDateFormatter`
and some other intl class instances can be serialized, but the
representation is meaningless, and unserialization yields uninitialized/
unusable objects. To prevent users from noticing this too late, we deny
serialization of such objects in the first place.
Closes GH-7945.
The hash is used to check whether the arginfo file needs to be
regenerated. PHP-Parser will only be downloaded if this is actually
necessary.
This ensures that release artifacts will never try to regenerate
stubs and thus fetch PHP-Parser, as long as you do not modify any
files.
Closes GH-5739.
