samples: add Terra samples

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

samples/Terra/luabridgeunion.t

@@ -0,0 +1,14 @@
+struct A { union {a : int, b : double}, c : int }
+
+terra foo(a : A)
+	return a.a + a.c
+end
+terra foo2(a : A)
+	return a.b + a.c
+end
+
+
+local test = require("test")
+
+test.eq( foo({a = 4, c = 6}), 10)
+test.eq( foo2({b = 4.4, c = 6}), 10.4)