Feature: Additon to dwarf, search order for units (as defined in the "uses" clause)

Dwarf does not contain any info about "cross unit scope". That is neither, which units are in scope (when starting from a given/current unit), nor in which order those units are to be searched.

This makes it impossible to find the correct declaration of some types.

Mind, this does not cause an issue for variables or types defined within the current unit, as they provide the info by having links directly to other dwarf elements.

But this affects

• global variables. They can be in other units, and the current unit may not contain info on them.
• type name that are not in the unit, but that the user uses to typecast his data. E.g. typecasting a "Sender" to "TMyForm" while not in the unit that has "TMyForm"