Add consistency checks during local dependency generation

[phdmakk]

In connection with #2, there might be some issues with the determination of the exact locations of certain module definitions. These shall be resolved by enforcing certain rules in the implementation of TTCN-3 test code. Subsequently there should be consistency checks that make sure the rules are enforced correctly while generating local dependencies, and if they are not, respective warnings and markers shall be produced to indicate the issues and their causes.

The simplest check could be to compare the locations of subsequent definitions, which may as well be sufficient in most scenarios, although its reliability will need to be evaluated. Regarding the output, we could produce a warning and instead of adding arbitrary markers in the line fields, include a distinct element attribute (i.e. "conflict", "warning", etc.) that indicates such issues (it may also provide additional information in this case).