[plt-scheme] 200.2

The exp-tagged code in CVS for MzScheme and MrEd is now version 200.2.

Changes:

 * Windows: launchers (executables that start MrEd- and MzScheme-based
   programs) are now applications that link directly to the MrEd and
   MzScheme DLLs. The old launchers were stub programs that lauched a
   separate MrEd or MzScheme process.

   The most visible result of this change is that the process manager
   will list DrScheme as "DrScheme.exe" instead of "MrEd.exe".

   The less visible benefits involve process ids and eliminating
   command-line length limits.

 * Windows: the tools for creating launchers and `mzc --[gui-]exe'
   executables now support custom icons for the resulting executable.

   For a launcher created by Setup PLT to load "x.ss", place "x.ico" in
   the same directory as "x.ss", and Setup PLT will install the icon.
   With `mzc --[gui-]exe', use the --ico flag.

 * Mac OS X: `mzc --[gui-]exe' now works. (Supply a Mac-format icon
   with --icns.)

 * Fixed mzc bug with `set!' on a module-defined variable.

Matthew