Extended testcases.

Extended two testcases with additional tests.
Support using scope operator as identifier.

The scope operator can now be used to resolve to the root object by
using the ‘@‘ operator.
X addr-mode was sometimes incorrectly selected

The algorithm that selects VM addressing mode selected the X (take
address of a register) in invalid cases, causing some operations to
crash.
Add tc_root01 testcase.

This testcase validates the various properties of the root object. Also
fixed a bug in the type::nameof metaprocedure that caused a crash when
db_nameof returned NULL.