Merge topic 'functional-callbacks'
8c92db82 MessageCallback: Remove unused bool& argument bcee24ae Use `std::function` for callbacks Acked-by:Kitware Robot <kwrobot@kitware.com> Acked-by:
vvs31415 <vstakhovsky@fastmail.com> Acked-by:
Daniel Pfeifer <daniel@pfeifer-mail.de> Merge-request: !2872