Access to unmatched named arguments

[gknowles]

When someone passes in a random switch there should be a way to see it, instead of always being an error (or ignored).

[gknowles]

Without knowing whether the argument takes a value or is just a flag there's no way to parse the rest of the line. It would be possible to call a user method for unknown options that returns either an error or enough info for parsing to continue, but is that actually something anybody wants?