Prep for handling list content with textutil:expander context buffers.
Not yet functional. See fmt_def for notes.
Draft of definition list buffer approach.
Definition list definitions are now pushed to context buffers, which are popped and formatted at the start of the next definition and at the end of list. This approach simplifies things (formatting is applied in one place, mddt_dlelement_end, instead of being spread across special cases in plain_text and list_end).

This breaks some formatted expected by existing tests, which now fail.

This method should be expanded to apply to all dl types (not just the plain def) as well as all (non-dl) list types.
Converted remainder of dl list types to use definition context buffers.
Markup tests pass. Two nesting tests still fail.
Dl definition context buffer begin proc now takes term title.
Simplifies calling: just mddt_dlelement_begin instead of also ex_cappend
Added MIT License file
renamed dlbuffer tests to broader listbuffers
draft test case for ol elements
move listbuffers test file to proper home in tests/
using buffers for enum list elements (draft)
updated some test cases to expect tabs for enum lists
expanded test cases for clarity; use explicit case ids
explicit test case ids for listbuffers tests
List buffers implemented; nesting formatting errors persist (newlines/indentation)
All list nest test now pass. One special-case formatting conditional (eg, a hack) is in place to insert a blank line before ol/ul lists nested in dls.
Factored common newline-trimming code into its own proc.
Added basic buffer test case for ul lists