[plt-scheme] v203.2

The exp-tagged code in CVS for MzScheme and MrEd is now version 203.2.

Changes:

 * Added UDP support. The essential procedures are

    (udp-open-socket) -> <socket>
    (udp? <v>) -> <boolean>

    (udp-bind! <socket> <address-str/#f> <port-k>) -> 
    (udp-connect! <socket> <address-str/#f> <port-k/#f>) -> 

    (udp-send-to <socket> <address-str> <port-k> <str> [<start-k> <end-k>]) ->
    (udp-send <socket> <str> [<start-k> <end-k>]) ->

    (udp-receive! <socket> <mutable-str> [<start-k> <end-k>]) ->
       -> (values <count-k> <from-address-str> <from-port-k>)

    (udp-close <socket>)

   See the documentation for information on other procedures.

   Thanks to Eduardo Cavazos for getting me started in the right
   direction.

 * Added `port-file-identity' for determing whether two open
   file-stream ports read from or write to the same device and file.

 * Added a syntax for listeral hash tables: #hash((<key> . <val>) ...)
   and #hasheq((<key> . <val>) ...). The former creates an immutable
   table with `equal?'-compared keys, the latter `eq?'-compared keys.
   Hash tables are printed using this notation when the new
   `print-hash-table' parameter is set to #t. The new
   `make-immutable-hash-table' procedure constructs an immutable table
   dynamically.

 * Added a syntax for literal regexp values: #rx<string>. The printer
   always uses this format.

 * Added `application-quit-handler' to MrEd.

Matthew