Add an attribute to the namespace to distinguish namespace; stmt; from namespace {stmt;}

[TysonAndre]

(e.g. getAttribute('namespaceHasBracket') : bool

This will help people writing code pretty printers, visualizers, transformers, etc

Mentioned in TysonAndre/php-parser-to-php-ast#10

[nikic]

Attribute added in 5a9fbca. I'm using kind following a convention used by a number of other nodes.