Prior to version 2.1 -- General in-house development of PBIO

Version 2.1  -- First official release

Version 2.2  -- Nov 15, 1996
	Changed PBIO wire format from format version 4 to format version 5 as
	part of heterogeneity enhancements.  Documented dynamic array support
	and error routines.

Version 3.0  -- April 23, 1997
	First official support for Windows NT platforms.  Better support for
	replacing the bottom level of I/O with other connected and reliable
	transport mechanisms.  Functioning, but yet-undocumented release of
	IOContexts, which support a memory-to-memory encoding and decoding of
	data structures.  Contexts are used to support non-connected
	transport layers and protocol tunneling.  (Caveat: The contexts
	interface may evolve slightly as we gain experience with it.)
	!! User visible change !!  The `flags' parameter to open_IOfd() and
	open_IOfile() no longer takes the same values as the Unix open()
	system call.  Instead substitute "r" to open a file for reading and
	"w" to open a file for writing.

Version 3.1  -- June 2, 1997
	Release containing documentation and support for non-connected
	transports.  Minor changes to previous interface to these transports.
