The `T.P.Lua.writeCustom` function changed to allow either a TextWriter
or ByteStringWriter to be returned. The global variables
`PANDOC_DOCUMENT` and `PANDOC_WRITER_OPTIONS` are no longer set when the
writer script is loaded. Both variables are still set in classic writers
before the conversion is started, so they can be used when they are
wrapped in functions.
The function can be used to convert a classic writer into a new-style
writer by setting it as the value of `Writer`:
``` lua
Writer = pandoc.write_classic
```
or to fully restore the old behavior:
``` lua
function Writer (doc, opts)
PANDOC_DOCUMENT = doc
PANDOC_WRITER_OPTIONS = opts
load(PANDOC_SCRIPT_FILE)()
return pandoc.write_classic(doc, opts)
end
```
Albert Krewinkel