CustChoice

I was looking into why the search dialog would no longer let me tab to
the search engine list and press down arrow to switch between them...
It seems that, once Jorge added a CustChoice in fltkui.cc, the dialog code
started to use _that_ one and not its own.

(I would've expected something to complain about there being two
CustChoice::handle()s in that case...)

Would it be considered incorrect in any way if fltkui.cc's CustChoice
and CustInput2 were put inside dw::fltk::ui?