Update to upstream version '8.8.3'
with Debian dir d29b0684aee82969a6d6eae4d7ad2978586886fb

Update to upstream version '8.8.2'
with Debian dir a91e096184cbf8323fd0fc3058cf2d13b2e17586

Instead traverse once at shutdown.

Inline iteration inside func(s *bState)

Commit d2d7398c allows to drop mutex book keeping.

This allows ranging over decorators concurrently without using mutexes
or other sync book keeping because next call to d.Decor() is awaited.

DecoratorAverageAdjust is very uncommon method to call because start
time can be set at construction time. It's not worth to keep slice for
method which is potentially never called.

fixes #142