GC tweaks

[Stephen Weeks]

> The gc code is not type correct: the function dfsPop() in GC_size.c returns a
> pointer and takes a single GC_state argument.  It is  passed  to  maybeCall()
> and  GC_foreachPointerInObject(),  which requires it to take 2 arguments, the
> second one being a (pointer *) and to return void.
> 
> This could actually cause bad code, although it is unlikley.   I  don't  know
> why  GCC  didn't detect this, but my guess is that it doesn't check the types
> on function pointers.

I am confused.  The only thing I see that you could be talking about is line 149
of GC_size.c, which is

		GC_foreachPointerInObject(s, dfsPushIfMarked, dfsPop(s));

That looks type correct to me.