Strictly speaking this is not a true deduplication; the test output will be
slightly different (due to inconsistent print statements) but I think this is
close enough.
- Add height parameter to z_importkey to reduce rescan range
- Change semantics of rescan parameter, so users can explicitly force a rescan
for existing keys.
Closes#2032
Per Grön
Daira Hopwood
Jack Grigg
Sean Bowe