function pointer to the vga render dispatch table and initialized it with
vga_nop. The problem is that vga_nop() is a varargs function, and the
table declares a non-varargs function pointer. On amd64 (and I think ppc),
mixing varargs and non-varargs function pointers is fatal.
Change vga_nop() and gfb_nop() from varargs to non-varargs do-nothing
functions. This stops the stack corruption that only happened on amd64.
Approved by: re (scottl)
e55b30b469