* Add WSDISPLAY_TYPE_VESA for vesafb. While here, fix a typo in a comment.
* Add WSDISPLAYIO_SSPLASH and WSDISPLAYIO_SPROGRESS ioctls. The former
toggles the splash screen on and off, and the latter updates the progress
animation.
* Prevent more than one hw driver from claiming to be the console.
* In vcons, keep two pointers to the screen's vcons_data. This lets us
override the original (ie with null emulops during boot), and restore
them later on.