samples: add Terra samples

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

samples/Terra/for2.t

@@ -0,0 +1,31 @@
+
+terra foo(a : uint64, s : uint64)
+    var r = 0
+    for i : uint64 = 0,a,s do
+        r = r + i
+    end
+    return r
+end
+
+terra foo2(a : int)
+    var r = 0
+    for i : int = 0.f,a do
+        r = r + i
+    end
+    return r
+end
+terra foo3(a : int)
+    var r = 0
+    for i = a,0,-1 do
+        r = r + i
+    end
+    return r
+end
+
+
+local test = require("test")
+test.eq(foo(10,1),45)
+test.eq(foo(10,2),20)
+test.eq(foo(0,1),0)
+test.eq(foo2(10),45)
+test.eq(foo3(10),55)