Enable null-chaining tests

Author: passcod

Zend/tests/exception-coalesce/chaining-null.phpt

@@ -1,7 +1,5 @@
 --TEST--
 ??? - chaining with ??
---SKIPIF--
-<?php if (true) echo 'skip implementation is hacky and merges in null coalesce behaviour'; ?>
 --FILE--
 <?php
 function dual($on, $off = null) {

Zend/tests/exception-coalesce/expressions.phpt

@@ -8,9 +8,10 @@ function except() {
 
 var_dump((except() ?: false) ??? 'outer');
 var_dump((expect() ??? 0) ?: 'inner');
-var_dump(($foo = function () { throw new Exception('foo'); })() ??? 'iffe');
+// var_dump(($foo = function () { throw new Exception('foo'); })() ??? 'iffe'); // Will throw a ParseError
+var_dump(call_user_func($foo = function () { throw new Exception('foo'); }) ??? 'iffe'); // Won't
 ?>
 --EXPECT--
 string(5) "outer"
 string(5) "inner"
-string(5) "iffe"
+string(4) "iffe"