Redesign ports. New design supports bidirectional ports. Old code

Redesign ports.  New design supports bidirectional ports.  Old code
should continue to work, with two (unlikely) exceptions: the
input/output port pairs for sockets and processes are now implemented
as bidirectional ports, and closing one of the ports automatically
closes the other as well.

* New procedures:

	CLOSE-PORT
	I/O-PORT?
	MAKE-GENERIC-I/O-PORT
	MAKE-I/O-PORT
	OPEN-I/O-FILE
	PORT/COPY
	PORT/INPUT-CHANNEL
	PORT/OPERATION
	PORT/OPERATION-NAMES
	PORT/OUTPUT-CHANNEL
	PORT/STATE
	PORT?
	SET-PORT/STATE!
	SUBPROCESS-I/O-PORT

* New global variable CONSOLE-I/O-PORT identifies the bidirectional
  port that communicates with Scheme's console.  CONSOLE-INPUT-PORT
  and CONSOLE-OUTPUT-PORT are initially EQ? to this port.

* Obsolete procedures:

	Old name			New name
	----------------------------	--------------------
	INPUT-PORT/CHANNEL		PORT/INPUT-CHANNEL
	INPUT-PORT/COPY			PORT/COPY
	INPUT-PORT/CUSTOM-OPERATION	PORT/OPERATION
	INPUT-PORT/OPERATION		PORT/OPERATION
	INPUT-PORT/OPERATION-NAMES	PORT/OPERATION-NAMES
	INPUT-PORT/STATE		PORT/STATE
	OUTPUT-PORT/CHANNEL		PORT/OUTPUT-CHANNEL
	OUTPUT-PORT/COPY		PORT/COPY
	OUTPUT-PORT/CUSTOM-OPERATION	PORT/OPERATION
	OUTPUT-PORT/OPERATION		PORT/OPERATION
	OUTPUT-PORT/OPERATION-NAMES	PORT/OPERATION-NAMES
	OUTPUT-PORT/STATE		PORT/STATE
	SET-INPUT-PORT/STATE!		SET-PORT/STATE!
	SET-OUTPUT-PORT/STATE!		SET-PORT/STATE!
	SUBPROCESS-INPUT-PORT		SUBPROCESS-I/O-PORT
	SUBPROCESS-OUTPUT-PORT		SUBPROCESS-I/O-PORT

  For now these procedures still exist.

* Obsolete input-port operations:

	Old name		New name
	---------------		---------------------
	BUFFER-SIZE		INPUT-BUFFER-SIZE
	BUFFERED-CHARS		BUFFERED-INPUT-CHARS
	CHANNEL			INPUT-CHANNEL
	SET-BUFFER-SIZE		SET-INPUT-BUFFER-SIZE

  INPUT-PORT/OPERATION and INPUT-PORT/CUSTOM-OPERATION perform these
  translations so your programs should continue to work.

* Obsolete output-port operations:

	Old name		New name
	---------------		---------------------
	BUFFER-SIZE		OUTPUT-BUFFER-SIZE
	BUFFERED-CHARS		BUFFERED-OUTPUT-CHARS
	CHANNEL			OUTPUT-CHANNEL
	SET-BUFFER-SIZE		SET-OUTPUT-BUFFER-SIZE

  OUTPUT-PORT/OPERATION and OUTPUT-PORT/CUSTOM-OPERATION perform these
  translations so your programs should continue to work.

* The ASSOCIATED-PORT operation is no longer implemented by any
  runtime system port.  Ports that previously supported this operation
  are now bidirectional.

* WITH-INPUT-FROM-FILE and WITH-OUTPUT-TO-FILE no longer close the
  port when they are exited abnormally.

* Change cold-boot sequence to permit records to be used in most of
  runtime system.

* New procedure RECORD-COPY.

* New files "genio.scm", "fileio.scm", and "ttyio.scm" replace old
  files "genin.scm", "genout.scm", "filein.scm", "filout.scm",
  "ttyin.scm", and "ttyout.scm".

* New file "port.scm".