samples: add Terra samples

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

samples/Terra/overloadmethod3.t

@@ -0,0 +1,18 @@
+
+struct A { a : int }
+A.methods.foo = terra(self : A)
+	return 2
+end
+
+terra A:foo() 
+	return 1
+end
+
+
+terra doit()
+	var a = A { 3 }
+	var pa = &a
+	return a:foo() + pa:foo()
+end
+local test = require("test")
+test.eq(doit(),4)