samples: add Terra samples

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

samples/Terra/zeroreturn.t

@@ -0,0 +1,18 @@
+
+
+local b = global(0)
+
+terra foo(a : int)
+	if a > 3 then
+		return
+	end
+	b = a
+end
+
+terra getb() return b end
+
+local test = require("test")
+foo(4)
+test.eq(getb(),0)
+foo(2)
+test.eq(getb(),2)