Mlt_parser contains functions for parsing *.mlt files, which contain
OCaml toplevel sessions -- i.e., a series of statements followed by
their output (in the form of expect
tests).

The first of these functions, split_chunks, was extracted out of
Toplevel_expect_test,
where it's used to divide the toplevel session into "chunks", where
each chunk comprises a set of toplevel code phrases (statements
separated by ;;) and the expect test they precede.

The second, parse, is used by a tool that converts *.mlt files
into *.org files. That tool needs to be able to distinguish OCaml
code phrases, expect tests, and blocks of org-mode markup (delimited
by [%%org] annotations).