Merge commit '991539725e5943b7f280f7ecd7a00aa7f3dc0582'
Merge commit '5ce9683858f5ced8b0df665aad74271dc7c9648d'
Merge branch 'develop'
removed comparison with 0

The concept is supposed to generalize pointers and optional<>, but the latter has abandoned the comparison with 0 a long while ago.
Merge branch 'patch-1' of github.com:akrzemi1/utility into akrzemi1-patch-1
Merge branch 'akrzemi1-patch-1' into develop