Module signature LocatableConfig

A signature module that allows cross language support for locatable elements in a query language, for instance C++ or Java.

This module, and qtil modules that depend on it, should already have preexisting language-specific implementations in the qtil modules for each language, so that you don’t have to implement it yourself, for instance, in qtil.Cpp or qtil.Java. However, implementing this module allows you to add qtil support for new languages.