#4 implement class / namespace symbol registration

[Andre Baresel]

The parser needs to be extended to add special nodes
for the symbols and the identifier resolver needs to be
extended for registering class / namespace identifiers.

Tests need to be written which find out locations of
class name uses (every appearance need to be detected).

An implementation for hierarchical identifier
namespaces is allready provided by the class
'IdentifierScope' which can register and lookup symbols
in C++ style (with the scope operator '::').