Permission to merge bug fix to Outcome

From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2022-04-02 20:20:33

Issue being fixed is https://github.com/ned14/outcome/issues/259 where 
enabling of move assignment was not calculated correctly.

(To be specific, if both T and E implement move assignment and default 
construction, but not move nor copy construction, we did not enable move 
assignment before and with this fix now we do)

Code fixing it is at https://github.com/ned14/outcome/pull/260

Fix passes on develop branch at 
https://www.boost.org/development/tests/develop/developer/outcome.html

Niall