Treat global constant declared using const keyword as global and not class constant

[tetsuo13]

Distinguish between const keyword used inside class definition and not (#50)

PHP 5.3.0 introduced behavior of using const keyword in place of define() for global constants. token_get_all() still treats it as a class constant however.

[avit]

I think this introduced a regression: const defined in a class now shows up as a global.

[tetsuo13]

I've duplicated this behavior. Trouble lies with the inherit limitations in using token_get_all(): it correctly identifies tokens but doesn't understand their parent/child relationships with other objects. For example, a class constant is identical to a global constant.

I'll try to either amend my previous commit or attempt at modifying PHPDoctor's parsing engine to add relationships -- the latter of which is probably needed in order to implement some of the other features requested in tickets.