[plt-scheme] Embedding mzscheme on cygwin - linking problems

Ittai and I have tracked down the problem: the garbage collector is
unable to find static variables in "libmzscheme.dll" and register them
as roots. (The same problem happens with Mac OS X.)

To avoid this problem when using Cygwin, start the embedding program
with

   scheme_set_stack_base(NULL, 1);


I'll add this information to "Inside MzScheme", of course.

Matthew