[arch-releng] Use pandoc instead of make-doc.sh

I would like to propose using pandoc ( http://johnmacfarlane.net/pandoc/ ) instead of the make-doc.sh script for converting the installation guide (Markdown syntax) to the document hosted in the wiki (MediaWiki syntax). I've tested it and the result looks pretty good, with only a few minor manual refinements required (which I volunteer to perform, if needed): instead of the current script, which practically produces an html document, we would get a correctly-formed, much neater MediaWiki document. This would greatly simplify further improvements in the wikification of the the guide, like the adaptation to ArchWiki's style standars. Thank you Dario