samples: add Terra samples

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

samples/Terra/incompletetypetest3.t

@@ -0,0 +1,13 @@
+
+
+struct A {
+	a : int
+}
+
+
+terra what()
+	var a : &A = nil
+	return a - a
+end
+
+what:compile()