added test case; threadex example crashes now

tests/threads/tracy_allocator.nim

@@ -0,0 +1,25 @@
+discard """
+  output: '''true'''
+"""
+
+var somethingElse {.threadvar.}: ref string
+
+type MyThread = Thread[void]
+
+proc asyncThread() {.thread.} =
+  new somethingElse
+
+var threads = newSeq[ptr Thread[void]](8)
+
+for c in 1..1_000:
+  #echo "Test " & $c
+  for i in 0..<threads.len:
+    var t = cast[ptr Thread[void]](alloc0(sizeof(MyThread)))
+    threads[i] = t
+    createThread(t[], asyncThread)
+
+  for t in threads:
+    joinThread(t[])
+    dealloc(t)
+
+echo "true"