[Boost.MSM] Please, update master with changes from develop
I just stumbled across a compilation-error with the latest Boost release
(1.71) of Boost.MSM for which I already provided a merge-request  a
year ago, and which was merged to "develop" branch at that time, too.
Still, the "master" branch lags this merge-request (and a lot more 
from former years which are in "develop") but has some other unrelated
merge-requests  merged in which are not in "develop".
I would love seeing "develop" being merged into "master" (and maybe
vise-versa) so that bugs for which fixes already exist will no longer be
present in the next Boost release.