Ambiguous AST node: implement resolve to variables

[ForNeVeR]

For more information on what is the "ambiguous AST node", see this discussion.

Currently, it only resolves to a declaration but not a variable definition. For example, this seems to be broken:

typedef int xxx;
xxx(foo); // declares a variable foo of type xxx, the same as "xxx foo;"

We should support this construct as well as the function call.

Look for the number 213 in the code to find clues to implement this feature.