Merge branch 'PHP-5.6'

* PHP-5.6:
  Revert "Fix bug #66568: the second arg for unserialize is optional." as we already reverted the introduction of the second arg.
Merge branch 'phpng' of https://git.php.net/repository/php-src into phpng
Use arena allocator (currently leaky!)
Fix leaks

Must find a good way to handle constant expressions...
Fix bugs
Replicate old linenos for class binding
Update error message
Fix code in test
Remove dead code
Add functions for create str/long ast directly
Remove DUMMY_STRINGL

What is that for?
Make lexer return AST nodes
zend_do_return -> zend_emit_final_return
Create namespace_name via AST
Add object initialization checks for sqlite3 classes
Merge branch 'PHP-5.6'

* PHP-5.6:
  Add object initialization checks for sqlite3 classes
Fix SPL objects initialization checks
Merge branch 'PHP-5.6'

* PHP-5.6:
  Fix SPL objects initialization checks
Fix missing type checks in various functions
Cleanup member modifier code