Fix bugs with default argument and implement the relevant test cases.

Test that demonstrate the "new 0" and show some other erroneus behaviour too.

Implemented CastExpression. ImplicitCast and ExplicitCast statement classes.

Fixed implicit constructor string generation.

Implemented CtorExpr.

All test cases pass.

Fixed indentations, streamlined the code.

Fixed regressions.

Fixed regressions.

Adding a test case not covered before.

Fixed, refactored and simplified things.

Still more fixes (0 to null ptr conversion, enum check). The additional test passes now too.