Reads a namespace name
```ebnf
namespace_name ::= T_NS_SEPARATOR? (T_STRING T_NS_SEPARATOR)* T_STRING
```
@see http://php.net/manual/en/language.namespaces.rules.php
@return {Reference}
function(resolveReference) {
    const result = this.node();
    let relative = false;
    if (this.token === this.tok.T_NAMESPACE) {
      this.next().expect(this.tok.T_NS_SEPARATOR) && this.next();
      relative = true;
    }
    const names = this.read_list(
      this.tok.T_STRING,
      this.tok.T_NS_SEPARATOR,
      true
    );
    if (
      !relative &&
      names.length === 1 &&
      (resolveReference || this.token !== "(")
    ) {
      if (names[0].toLowerCase() === "parent") {
        return result("parentreference", names[0]);
      } else if (names[0].toLowerCase() === "self") {
        return result("selfreference", names[0]);
      }
    }
    return result("classreference", names, relative);
  }