Requires microcode 11.50 and runtime 14.100.

Requires microcode 11.50 and runtime 14.100.

* Implementation of update optimizer, and direct use of termcap rather
  than the buggy curses.

* Extensive rewrite of display update code.  New display update
  scrolls lines in some cases, and is tuned to offset the added cost
  of running the update optimizer.

* New display update event-tracing facility for debugging.

* If the last line of the buffer is empty, and the previous line is
  completely visible, the modeline says that the bottom of the buffer
  is visible.

* Editor variables can have value validity tests, which are applied
  whenever the variable's value is altered.  If the test fails, an
  error is signalled, so that user code can depend on the variable's
  contents satisfying the validity test.

* `(buffer-point (current-buffer))' now equivalent to
  `(current-point)'.

* `window-redraw!' no longer takes a second argument.  It's new
  meaning is to force the window to be redrawn from scratch, without
  affecting the window starting point or cursor position.

* Removed procedures:
	window-end-index
	window-redraw-preserving-point!

* Changed `window-start-index' to `window-start-mark'.

* Change terminal state control to use new I/O port operations that
  extract channels, and perform the terminal controls directly on
  those channels.

* Internal flag `debug-internal-errors?' facilitates debugging Edwin
  if set true.  Normally this is false.

* When first starting the editor, the default behavior is to try to
  use Scheme's controlling terminal, and if that isn't available, to
  use X.  If Scheme is started under Emacs, it has no controlling
  terminal, and therefore it will use X.