more docs, fixes, examples

examples/coroutines3-crit.csn

@@ -1,16 +1,21 @@
 (
     ; This example shows the use of critical sections.
 
+    ; Set short timeslice (50us) to make the effect more pronounced
+    (rt-opt RT_TIMESLICE 50)
+
     (spawn _ unsafe 'A' 'Z')
-    (spawn _ safe '0' '9')
-    (ssleep 2)
+    (spawn _ unsafe 'a' 'z')
+    (spawn _ safe '0' '9') ; Notice that the sequence 0-9 is always printed in its entirety - because it is in a critical section
+    (msleep 200)
+    (halt)
 
     (proc unsafe start end
         ; This can be interrupted any time
         (:x)
+        (yield)
         (ld r0 start)
         (:l)
-            (msleep 5)
             (ld @cout r0)
             (cmp r0 end)
             (j.eq :x)