term_hack is only needed in ocvm. also now fastty clears the screen

modules/drivers/fastty.lua

@@ -1,4 +1,4 @@
-_G.term_hack = true
+_G.term_hack = false
 function tty(gA,sA,sI,mx,my)
  spawn("fastty: "..gA:sub(1,8)..","..sA:sub(1,8)..","..sI,function()
   _G.nlog = ""
@@ -9,6 +9,7 @@ function tty(gA,sA,sI,mx,my)
   gpu.bind(sA)
   local sx, sy = gpu.maxResolution()
   sx, sy = mx or sx, my or sy
+  gpu.fill(1,1,sx,sy," ")
 
   local function wl(s)
    s=tostring(s) or ""