For the new 2.0-style command line options, we need to parse strings of
the type:
  ident:key=val[,...]
and
  key=val[,...]

This patch adds two new option builders for these two, which return
(ident, {key=val,}) and {key=val,} for the above two formats. It also
handles specially constructs of type “key” (val is set to True) and
“no_key” (val is set to False, and the ‘no_’ prefix is stripped).

Reviewed-by: imsnah