Split critcl commands "check(link)" and "compiling" into proper frontend and backend code.
Basic slice of static .critcl scanner into package "critcl-scan".
Todo: Rework the scanner internal state.
Todo: Fix the back-references into the core
      (slice: meta data management, general utilities).
internal notes
critcl::scan - Resorted internals a bit, and fixed the handling of the main config+state.
Split a few general utilities into a low-level package.
Use this in core and other parts.