Reads a use statement
```ebnf
use_statement ::= T_USE
use_type? use_declarations |
use_type use_statement '{' use_declarations '}' |
use_statement '{' use_declarations(=>typed) '}'
';'
```
@see http://php.net/manual/en/language.namespaces.importing.php
@return {UseGroup}
function() {
    let result = this.node("usegroup");
    let items = [];
    let name = null;
    this.expect(this.tok.T_USE) && this.next();
    const type = this.read_use_type();
    items.push(this.read_use_declaration(false));
    if (this.token === ",") {
      items = items.concat(this.next().read_use_declarations(false));
    } else if (this.token === "{") {
      name = items[0].name;
      items = this.next().read_use_declarations(type === null);
      this.expect("}") && this.next();
    }
    result = result(name, type, items);
    this.expect(";") && this.next();
    return result;
  }