Add namespaced classes for the PHP Parser

[keesiemeijer]

In e482b28d6cb3761f0a2d69a2ea97fd19a0b22e7a the phpdocumentor/reflection requirement was updated to version 3. This change also updated the nikic/php-parser requirement (from phpdocumentor/reflection) to version 1.

In that version of the PHP Parser all classes changed by using namespaced names with the PhpParser vendor prefix.

The old non namespaced classes are still supported, but are not recommended. They are pointed to the name spaced versions with a class alias.

This PR updates all uses of PHP Parser classes to their namespaced versions.

[kkmuffme]

It's currently already at v5 already

@iandunn are you able to merge PRs/create releases? If yes, could @keesiemeijer perhaps update this PR for reflector v5 and we finally release an update with updated dependencies.