[plt-scheme] 299.9

The v299-tagged code for MzScheme and MrEd in CVS is now version 299.9.
(The exp-tagged coded remains version 207.1.)

The changes are minor:

 * Changed (one more time) `convert-evt' to `wrap-evt', and
   `finish-evt' to `handle-evt'.

 * Added `print-unreadable' parameter. If this parameter is set to #f,
   then an exception is raised when attempting to `write' a value that
   has no readable form.

 * Changed module expansion/compilation so that it's deterministic, as
   long as macros do not use `gensym' or external side-effects. Using
   `generate-temporaries' preserves determinism.

 * Changed `file-stream-buffer-mode' to work on input ports.

 * Changed internal strategy for evaluating `quote-syntax' expressions.

Matthew