Changes for International keyboards on win32 systems.

Changes for International keyboards on win32 systems.

ntscreen changed to work better with international keyboards.  The
changes peek into the event queue to see how the key presses have been
translated into characters.  Modifiers are also tracked to enable them
to be detected in parallel with keyboard translations (so that
modifier chords like C-M- are detected).

Characters now have 16 bits of character code (instead of 7) to allow
8-bit ISO latin and Unicode characters.  Strings are still based on
8-bit characters.

Runtime changed to allow these `wide' characters to be written and
read e.g. #\<code62834>

Edwin modes changed to treat characters in the range 128-255 as normal
alphabetic characters (to enable accented characters).