==> Provide a much more complete set of setters and getters for different
value types in the prop_array_util(3) and prop_dictionary_util(3)
functions.
==> Overhaul the prop_data(3), prop_number(3), and prop_string(3) APIs
to be easier to use and less awkwardly named, Deprecate the old
awkward names, and produce link-time warnings when they are referenced.
==> Deprecate mutable prop_data(3) and prop_string(3) objects. The old
APIs that support them still exist, but will now produce link-time
warnings when used.
==> When the new prop_string(3) API is used, strings are internally
de-duplicated as a memory footprint optimization.
==> Provide a rich set of bounds-checked gettter functions in and a
corresponding set of convenience setters in the prop_number(3) API.
==> Add a new prop_bool_value(3) function that is equivalent to
prop_bool_true(3), but aligned with the new "value" routines in
prop_data(3), prop_string(3), and prop_number(3).