samples: add Terra samples

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

samples/Terra/structcast.t

@@ -0,0 +1,38 @@
+struct A { a : int }
+struct B {a : int, b : A}
+
+local D = tuple(double, A)
+
+terra anon()
+    var b : B
+    b.a = 4
+    b.b.a = 3
+    
+    var d : D
+    d._0 = 1.0
+    d._1.a = 2
+    
+    b = B(d)
+    
+    return b.a + b.b.a 
+end
+
+terra anon2()
+    var b  = B { b = A{ 2.0 }, a = 4 }
+    var b2 = B { a = 4, b = A{ 2.0 } }
+    var b3 = B{ 4, A{2.0} }
+    return b.a + b.b.a + b2.a + b2.b.a + b3.a + b3.b.a
+end
+
+terra anon3()
+    return {5,A{6}}
+end
+
+terra anon4()
+    var b = B(anon3())
+    return b.a + b.b.a
+end
+test = require("test")
+test.eq(anon(),3)
+test.eq(anon2(),18)
+test.eq(anon4(),11)