samples: add Terra samples

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

samples/Terra/zeroreturn2.t

@@ -0,0 +1,17 @@
+
+a = global(0)
+
+terra doit()
+	a = a + 1
+end
+terra geta()
+	return a
+end
+
+terra bar()
+	return doit()
+end
+
+bar()
+local test = require("test")
+test.eq(geta(),1)