Mostly just eliminating concatenation-reassignments by chaining
concatenations, reordering assignments to allow better use of bin.pack,
and using tables to store intermediate results before concatenating
them. Used strbuf as a quick fix in dhcp.lua. Eliminated some unused
string variables in vulns.lua.
Mostly splitting function summaries (the first paragraph of NSEdoc) from
the body of the description to make the summary indexes shorter and
easier to scan.
Also fixed some unbalanced code tags like <code>foo</table>