Add to asciidoc writer support for tables with merged cells

[trianon1983]

When i convert from html to asciidoc page with tables with merged cells lose their merging.
It is necessary to add support for colspan and rovspan in assidoc writer.
Thanks

[trianon1983]

[jgm]

Can you give the output you'd expect for this input?

[trianon1983]

yes, sure. in this example i am expecting the following

[trianon1983]

full example:
example.zip

[trianon1983]

note that the alignment in the cells also does not work correctly

[jgm]

OK. Currently we convert the table to a "legacy table" which doesn't support colspans. The new pandoc AST does support colspans for tables, but it will take some work to convert the asciidoc writer to use this more complex representation. It's not a high priority for me at the moment, but maybe someone else will want to take this on? The HTML writer uses this already, so lines 1086 and following of src/Text/Pandoc/Writers/HTML.hs may be helpful.