All "helper functions" are not part of the Lua code for module pandoc,
but are added in Haskell. The respective documentation section must
therefore be excluded from automatic regeneration.
Avoid highlighting of "strings" by deriving from
`text-mode-syntax-table`. This fixes missing highlighting in default.html5
tag attributes.
Define comment starting and ending sequences to allow use of M-q (auto-fill)
on comments.
The pandoc module documentation in doc/lua-filters.md was automatically
generated from `data/pandoc.lua`. A make target is provided which uses
a lua filter to update the documentation.
