Jumbo options dupe-check bugfix.
I reverted too much in 945be4a... some Jumbo-specific stuff re-added
(namely, support for using \xHH notation in rules and ranges), now with
comments.

I'm not sure why that last mod is needed, versus core. It's origin is
b901293... I just have to trust myself on that one.
Deprecate "ansi" in encoding list output. We still support it as a shorthand
for ISO-8859-1 although it's ambiguous. Add support for "latin1" as another
alias for the same, even though that is still somewhat ambiguous :-P
WIP for ADL/NVML mapping to our device id (#750)