Fix for the extension parsing bug, as well as some extra checks for unsetting US country codes from other forks.
Fix for the extension parsing bug, as well as some extra checks for unsetting US country codes from other forks.

lukebeer/libphonenumber-for-php,sudiptpa/libphonenumber-for-php,giggsey/libphonenumber-for-php,gencer/libphonenumber-for-php,Xephi/libphonenumber-for-php,BenMorel/libphonenumber-for-php,digideskio/libphonenumber-for-php