Add initial 'language' definition for irc logs, extend color scheme.

The 'pack' version is generated from a highlightjs tree,
and must be used (as opposed to minimized source, this is packed)
in order to have fields/etc align with current highlightjs.

Will likely replace our highlightjs entirely in the near future,
incorporating this highlighting, but will keep the unpacked
language definition for reference/updates.
linkify 'link_url' classified items
Rebuild unified highlightjs using new 'irc' language def.

Filename indicates git commit of highlightjs version used,
all languages included (which I believe is same as before).