samples: add Terra samples

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

samples/Terra/macrolet.t

@@ -0,0 +1,17 @@
+
+
+twice = macro(function(a)
+	return quote
+		var v = a
+	in
+		v + v
+	end
+end)
+
+
+terra foobar()
+	var what = 1
+	return twice([quote what = what + 1 in what end]) + what
+end
+
+assert(6 == foobar())