Description:
------------
new DateTimeZone crashes apache when given something it can't recognize.

timezone_open is more robust

This has similar symptoms to Bug #43377 ; but is probably different

Reproduce code:
---------------
<?php

$dt = timezone_open("Australia/Adelaide");
var_dump($dt);

$dt = timezone_open("");
var_dump($dt);

$dt = timezone_open(null);
var_dump($dt);

$dt = new DateTimeZone("Australia/Adelaide");
var_dump($dt);

$dt = new DateTimeZone("");
var_dump($dt);

$dt = new DateTimeZone(null);
var_dump($dt);



Expected result:
----------------
object(DateTimeZone)#1 (0) {
}
bool(false)
bool(false)
object(DateTimeZone)#1 (0) {
}
bool(false)
bool(false)


Actual result:
--------------
object(DateTimeZone)#1 (0) {
}
bool(false)
bool(false)
object(DateTimeZone)#1 (0) {
}