samples: add Terra samples

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

samples/Terra/forp.t

@@ -0,0 +1,21 @@
+struct Range {
+    a : int;
+    b : int;
+}
+Range.metamethods.__for = function(syms,iter,body)
+    return syms, quote
+        var it = iter
+        for [syms[1]] = it.a,it.b do
+            body
+        end
+    end
+end
+
+terra foo()
+    var v = Range { 0, 3 } 
+    var vp = &v
+    var i = 0
+    for e in vp do i = i + e end
+    return i
+end
+assert(3 == foo())