moving i/o buffers back into kernel space

[utzoo!decvax!ucbvax!william]

The problem with the buffer mapping only applys to 
anything which occupies  KDSA5 (KISA5) and gets touched
at at clock interrupt pri. If you never use  anything
there, you don't need spl's at all. If you must use
it you can save it and restor it in trap(mch.s) at
interrupt time. We almost did that but for fear of permenantly
breaking  adb. We have since fixed adb. We also played
with the idea of savingt it in the context of a proc
so you could use it for other things as well.


	bill