* Empty '0' lines should not be passed to linesolvers.

* Completed lines should not be passed to linesolvers.

* fcomp: allow base index to increment.

* When a linesolver is given a complete line, and it reports that
  there is no inconsistency, the main solver should set the line's
  rank to zero, as no other linesolvers should be necessary.

* fcomp: show solid offsets in trace for DRAWING state.

* fcomp: make trace go through log output.

* Allow workings of line solver to be reported to the display. Should
be much easier now, since each linesolver can be given its own private
configuration context.

* Use strtoul instead of sscanf.
