Undisplayed new_member_options bits are reset whenever the General Options page is submitted.

[Mark Sapiro]

The code in Mailman/Gui/General.py for setting new_member_options doesn't take into account the fact that there might be option bits other than 'hide', 'ack', 'notmetoo' and 'nodupes' that are set, and it resets them even if the four displayed options are unchanged. This also affects bin/config_list which cannot set bits other than those 4 unless set via mlist.new_member_options =.