Use only on0/os0/on1/os1 options with PayPal.

According to these URLs:
https://www.paypal.com/cgi-bin/webscr?cmd=p/xcl/rec/options-help-outside
https://developer.paypal.com/webapps/developer/docs/classic/paypal-payments-standard/integration-guide/Appx_websitestandard_htmlvariables/

only two Options are supported via PayPal. I was fooled initially
because other fields *did* come through and *did* show up on the web
interface, but they are *not* accessible via the SOAP interface.

Therefore, I've switched to using the hack described here:
https://ppmts.custhelp.com/app/answers/detail/a_id/298/kw/soap%20gettransactiondetails%20option

to get 4 fields of data for Supporter transactions.