PHP-868: Make php_mongo_is_valid_id() static and use const arg
PHP-868: Check string pointer and length in php_mongo_is_valid_id()
Merge pull request #11 from jmikola/PHP-868-validate-mongodid

PHP-868: Inline php_mongo_is_valid_id() and use const arg

* jmikola/PHP-868-validate-mongodid:
  PHP-868: Check string pointer and length in php_mongo_is_valid_id()
  PHP-868: Make php_mongo_is_valid_id() static and use const arg