print_wiki: Fixes, explanation re. flash chips, links to footnotes.

 - Escape mainboard notes in the wiki output with <nowiki> (this became
   necessary because MediaWiki started to convert <mark@zl2tod.net> to <mark>).
 - Add explanations at the top of the flash chip table in the wiki.
 - Add links to the footnotes of mainboards and laptops similarly to
   what MediaWiki does: link from the reference to the footnote and
   vice versa too. Also, check for truncations of the footnotes due
   to the limited buffer.
 - Fix a typo introduced in r1555.

Signed-off-by: Stefan Tauner <stefan.tauner@student.tuwien.ac.at>
Acked-by: Stefan Tauner <stefan.tauner@student.tuwien.ac.at>

git-svn-id: svn://flashrom.org/flashrom/trunk@1694 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1