For now, SGC must be used, but `configure' does not select it
automatically.
Also, support Cygwin (in addition to MSYS) as a build environment
when using MinGW compilers. Since I build in a Cygwin environment
(which seemed to be the easiest way to get MinGW-w64 gcc), I use
../configure --host=x86_64-w64-mingw32 --enable-sgc
Ports must be forced closed in the case of kill a place,
and the existing code takes care of that.
The Windows fix is especially needed for the new places port
handling, but it turns out that the console handlign was broken for
places anyway.
GRacket registers witht a global table to indicate that
no transform is needed. (This change was intended to address
a 64-bit problem on Lion. It didn't help, but this seems
better than ignoring an error.)
