Update tv11 emulator and throttle it to use less host CPU.

The -s argument is number of milliseconds to sleep ever 1000 PDP-11
instructions.

build/pdp10-ka/start

@@ -25,7 +25,7 @@ gt40() {
 }
 
 tv11() {
-    (sleep 3; tools/tv11/tv11 -p 10011 localhost >tv11.log 2>&1) &
+    (sleep 3; tools/tv11/tv11 -s 4 -p 10011 localhost >tv11.log 2>&1) &
     started TV-11 "$!"
 }