tests: add debugobsolete calls before many obslog calls As requested by Pierre-Yves. The main reason is to catch superfluous creation of obsmarkers, as well as any future changes to how the obsmarkers get created.

stablerangecache: sanity check subranges Try to detect invalid conditions on insert as would result in deep recursions and final aborts much later. This has been observed on two different machines and the check makes it hopefully possible to find the origin of the problem.