Merge structures when combining DBs.
Add tests for merging DBs.
Sereal needs encoder and decoder.
Generate golden results in separate processes.
Quieten merge tests.
Regenerate golden results.
Try to impose order on STDOUT and STDERR.
New golden results with better STD* ordering.
Tidy Test code.
Don't run change.t and md5.t below 5.10.

In 5.8.[2-9] there is an error on non-threaded perls with "can't locate
structure for statement", and I can't be bothered track it down and fix or
work around it.  Let's just bump the minimum recommended version to 5.10, and
keep 5.6.1 and 5.8 as "best effort".
Regenerate golden results for change.t and md5.t.
Quieten DB merges.
Update Changes.
Store complex test results in specific databases.