_vcomp_fork stack frame puzzle

[Dan Kegel]

Using varargs like Andre tried doesn't work because pushing a va_list
isn't the same as pushing a list of arguments.
So I think we need assembly.  The assembly I gave earlier is wrong
because it cleans up the stack, which it's not allowed to do.
I've attached an updated patch to
http://bugs.winehq.org/show_bug.cgi?id=26688
with a _vcomp_fork that works for simple loops with and without
bound variables.

I guess the next step is porting the serial stub for _vcomp_fork to 64 bits.