add eval and potentially speed up variable access speeds when multi threading. fix bug in threading count

tests/multi_threading.ar

@@ -0,0 +1,14 @@
+let mythread(threadID) = do
+    term.log(threadID, "start")
+    let mynumber = 10
+    for (i from 0 to 1e4) do
+        mynumber += 1
+        mynumber
+    return term.log(threadID, "done")
+
+let threads = []
+term.time("start")
+for (i from 0 to 100) do
+    threads.append(thread(()=mythread(i)))
+    threads[i].start()
+term.timeEnd("start")