Now that core exports "option" as a synonym for option::t, search-and-
replace option::t with option.
The only place that still refers to option::t are the modules in libcore
that use option, because fixing this requires a new snapshot
(forthcoming).
Use ifaces instead of objs, stop wrapping everything in two (or three)
layers of no-value-added indirection, and remove some of the more
pointless/outdated idioms from the code.
