samples: add Terra samples

source: https://github.com/zdevito/terra/tree/master/tests

samples/Terra/fact.t

@@ -0,0 +1,16 @@
+local test = require("test")
+
+local Num = int
+local terra fact(a : Num) : Num
+    var c,i = 1,1
+    while i <= a do
+        c = c * i
+        i = i + 1
+    end
+    return c
+end
+
+
+test.eq(fact(1),1)
+test.eq(fact(2),2)
+test.eq(fact(3),6)