samples: add Terra samples

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

samples/Terra/class2.t

@@ -0,0 +1,45 @@
+local Interface = require("lib/golike")
+
+local I = Interface.create {
+	get = {} -> int;
+	set = int -> {};
+}
+
+struct A {
+	data : int
+}
+
+terra A:get()
+	return self.data
+end
+
+terra A:set(a : int)
+	self.data = a
+end
+
+struct B {
+	data : int
+}
+
+terra B:get()
+	return self.data + 1
+end
+
+terra B:set(a : int)
+	self.data = self.data + a
+end
+
+
+terra anInterface(a : I)
+	a:set(3)
+	return a:get()
+end
+
+terra foo()
+	var a = A { 0 }
+	var b = B { 2 }
+	return anInterface(&a) + anInterface(&b) 
+end
+
+local test = require("test")
+test.eq(foo(),9)