Add `submsetseq` function
This merge requests adds the submsetseq function, which for a list l computes all lists l' such that l' ⊆+ l. It also adds a new lemma about interleave.
Edited by Marijn van Wezel
This merge requests adds the submsetseq function, which for a list l computes all lists l' such that l' ⊆+ l. It also adds a new lemma about interleave.