first steps to thread local heaps

tests/accept/run/tnodeadlocks.nim

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+discard """
+  outputsub: "101"
+"""
+
+import os
+
+const
+  noDeadlocks = defined(system.deadlocksPrevented)
+
+var
+  thr: array [0..5, TThread[tuple[a, b: int]]]
+  L, M, N: TLock
+
+proc doNothing() = nil
+
+proc threadFunc(interval: tuple[a, b: int]) {.procvar.} = 
+  doNothing()
+  for i in interval.a..interval.b: 
+    when nodeadlocks:
+      case i mod 6
+      of 0:
+        Aquire(L) # lock stdout
+        Aquire(M)
+        Aquire(N)
+      of 1:
+        Aquire(L)
+        Aquire(N) # lock stdout
+        Aquire(M)
+      of 2:
+        Aquire(M)
+        Aquire(L)
+        Aquire(N)
+      of 3:
+        Aquire(M)
+        Aquire(N)
+        Aquire(L)
+      of 4:
+        Aquire(N)
+        Aquire(M)
+        Aquire(L)
+      of 5:
+        Aquire(N)
+        Aquire(L)
+        Aquire(M)
+      else: assert false
+    else:
+      Aquire(L) # lock stdout
+      Aquire(M)
+      
+    echo i
+    os.sleep(10)
+    when nodeadlocks:
+      echo "deadlocks prevented: ", deadlocksPrevented
+    when nodeadlocks:
+      Release(N)
+    Release(M)
+    Release(L)
+
+InitLock(L)
+InitLock(M)
+InitLock(N)
+
+proc main =
+  for i in 0..high(thr):
+    createThread(thr[i], threadFunc, (i*100, i*100+50))
+  joinThreads(thr)
+
+main()
+