set "<opt>_given" for each opt on the commandline

set "<opt>_given" for each opt on the commandline

For every option <opt> given on the commanline, in the output hash of
Parser#parse (and thus Trollop.options), in addition to setting
<opt> to the value given, set <opt>_given to true. This is useful if you need
to know which arguments were actually specified on the commandline, e.g. for
situations where arguments can override other arguments when given.