Add support for serializing to, and de-serializing from, JSON, as
specified in RFC 8259. Format is automatically detected for input,
and can be specified explicitly for output. The default format remains
XML.

As part of this change, generic prop_object_{internalize,externalize}()
functions are provided, and the "_with_format" flavor allows the output
format to be specified. Previous array- and dictionary-specific routines
remain for backwards compatibility.

branches: 1.10.12;
Improvements to the problib(3) API:

==> 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).

branches: 1.9.12;
Use .Fn to refer a function name instead of Nm.
Also, use Xr to refer problib(3) in the HISTORY section instead of Nm.

While parsing the man pages, any .Nm occurrence gets replaced by the
value specified in the NAME section. Referencing individual function
names with .Nm was causing makemandb(8) to replicate the complete
NAME section for every such occurrence. This was leading to an
ugly looking snippet in apropos(1)'s output when searched for
any of these man pages.

branches: 1.8.30; 1.8.34;
New sentence, new line. Use Dq.

Convert TNF licenses to new 2 clause variant

branches: 1.6.8;
boolean_t -> bool
TRUE -> true
FALSE -> false

branches: 1.5.4; 1.5.16;
Bump date for previous.

Several changes to proplib:
- Arrays can now be externalized and internalized in the same way
dictionaries can.
- Add new "externalize to file" and "internalize from file" functions
to make reading a property list from a file and writing a property
list to a file more convenient.
- Many assertions in the object implementations are gone. Instead,
calling an accessor for one object type with a different object type
as an argument will return a suitable "invalid" value.
- prop_object_type() now returns a new PROP_TYPE_UNKNOWN value if called
with a NULL object.
- Externalized property lists now contain a reference to the Apple XML
plist DTD.
- Add a new prop_ingest(3) facility, which provides a convenient way to
translate a dictionary into an arbitrary binary representation.

branches: 1.3.2;
Drop trailing whitespace.

- Add prop_array_equals(), prop_dictionary_equals(), and
prop_dictionary_keysym_equals(), and prop_object_equals() functions.
- Use realloc() where it makes sense. There will be more changes in this
area.
- Add a _prop_object_type structure that is used internally to keep
information about the object types. Decreases the footprint of the
objects slightly by replacing several pointers with just one.

Initial commit of proplib, a library for manipulating property lists and
converting to/from an XML external representation (based on Apple XML
property lists). Works in the kernel and user space.