Add QemuConsole parameter to vga_hw_*, so the interface allows to update
non-active consoles (the actual code can't handle this yet, see next
patch).  Passing NULL is allowed and updates the active console, like
the functions do today.

While touching all vga_hw_* calls anyway rename that to the functions to
hardware-neutral graphics_hw_*
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>