[css] Unescaping escape sequences

[Bjoern H. <der...@gm...>]

Hi,

  CSS::SAC currently does not unescape escape sequences, e.g. for

  e\xample { }

it reports a type selector for "e\xample" not "example". I don't think
it is necessary to report the difference to the application but it is
often necessary to unescape the tokens and I don't think the application
should do this, but rather CSS::SAC. If there is a need to maintain
escape sequences, there should be an option to explicitly request
unescaped tokens.