When changing screen saver parameters with wsconsctl (or any other way to

When changing screen saver parameters with wsconsctl (or any other way to
perform ioctls), check the flags of the currently displayed screen in order
to decide whether the screen saver needs to be retriggered, rather than the
flags of the device we are issuing the ioctl on.

wsconsctl will always use ttyC0, while the X server may run on another
virtual screen (such as ttyC4), and the kernel screen saver would then be
reenabled behind the X server's back.

While there, apply this `should the screen burner get reenabled or disabled?'
logic at the end of every virtual screen switch. The screen burner will now
get reenabled when switching from X11 to a virtual text console, and disabled
when switching back to X.