Okay... a real bug

[Stephen Weeks]

> Segfaults....  it just computes the sum of the first 100 integers.. I think
> this is a stack resize bug... 

Yes indeed.  There are two fencepost bugs (essentially the same) in
the stack limit check.  In machine.h, StackOverflowCheck should be
defined as

#define StackOverflowCheck (stackTop >= gcState.stackLimit)

And, in gc.c, stackTopIsOk should be defined as

static bool stackTopIsOk(GC_state s, GC_stack stack) {
	return stackTop(stack) < stackLimit(s, stack) + topFrameSize(s, stack);
}

With these two fixes, the program prints out 5051 (i.e. 1 + the sum of
the first 100 integers, which what I think your code is doing).  I
hope this fixes the problem, and keep those bug reports coming.