Update PhoneNumberUtil.php

There is  a side effect with the "not" operator.

Example :
* phone number : +33 6 76 83 51 85
* default country : DE


For the [PHP demo] (http://giggsey.com/libphonenumber/?phonenumber=%2B33+6+76+83+51+85&country=DE&language=fr&region=FR), the result of the method "isValidNumberForRegion()" is **true**

For the [Javascript Demo] (http://libphonenumber.googlecode.com/svn/trunk/javascript/i18n/phonenumbers/demo-compiled.html), the result of the method "isValidNumberForRegion()" is **false**

And the expected result is **false**, because +33 is the country code for France, not for Germany.