branches: 1.3.74;
struct plistref does not reference other proplib data types, so split it
in its own header file to be included by dkio.h. Fixes breakage due to
pollution from proplib.h in programs which include ioctl.h. Tested and OK
by dogcow@.

branches: 1.2.4; 1.2.12;
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: 1.1.2;
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.