samples: add Terra samples

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

samples/Terra/multiconstructor.t

@@ -0,0 +1,17 @@
+
+terra foo() : {double, double}
+	return 1.0,3.0
+end
+
+struct A {c : int, a : int, b : double }
+
+terra bar()
+    var r = foo()
+	var a  = A {1,unpackstruct(r)}
+	var b  = A {1,2,(foo())._0}
+	var c  = A {c = 1,a = 2,b = foo()._0}
+	return a.c + a.a + a.b + b.c + c.c
+end
+
+local test = require("test")
+test.eq(7,bar())