Adapt unwind tests for PHP 5.6 style error messages

PHP 5.6 has more detailed error messages, i.e. it says
"on null" instead of "on a non-object".  Replaced this
particular part by a %s match to match both possibilities
so the test suite passes on PHP 5.6 as well as older
versions.

tests/fatal_error_no_uninstall_inner_frame.phpt

@@ -27,4 +27,4 @@ $js->executeString("PHP.foo();");
 --EXPECTF--
 nothing.
 
-Fatal error: Call to a member function foo() on a non-object in %s/fatal_error_no_uninstall_inner_frame.php on line 15
+Fatal error: Call to a member function foo() on %s in %s/fatal_error_no_uninstall_inner_frame.php on line 15

tests/fatal_error_recursive.phpt

@@ -35,4 +35,4 @@ $js->executeString("PHP.nofail(); PHP.foo();");
 foo
 foo
 
-Fatal error: Call to a member function bar() on a non-object in %s/fatal_error_recursive.php on line 7
+Fatal error: Call to a member function bar() on %s in %s/fatal_error_recursive.php on line 7

tests/fatal_error_rethrow.phpt

@@ -23,4 +23,4 @@ $js->executeString($script);
 ?>
 ===EOF===
 --EXPECTF--
-Fatal error: Call to a member function bar() on a non-object in %s/fatal_error_rethrow.php on line 7
+Fatal error: Call to a member function bar() on %s in %s/fatal_error_rethrow.php on line 7

tests/fatal_error_uninstall_in_first_frame.phpt

@@ -29,4 +29,4 @@ $bar->foo();
 --EXPECTF--
 nothing.
 
-Fatal error: Call to a member function foo() on a non-object in %s/fatal_error_uninstall_in_first_frame.php on line 20
+Fatal error: Call to a member function foo() on %s in %s/fatal_error_uninstall_in_first_frame.php on line 20