
`sepby1` is a common reusable combinator in Haskell Parsec. This adds `mpc_sepby1(mpc_fold_t f, mpc_parser_t *sep, mpc_parser_t *a)` according to Haskell's implementation: https://hackage.haskell.org/package/parsec-3.1.16.1/docs/src/Text.Parsec.Combinator.html#sepBy1 Reuses existing `mpc_and`, `mpc_many`, and `mpcf_snd_free`.