databases/rrdtool: update to 1.4.8

- Update to 1.4.8 [1] (based on)
- Allow staging

PR:		ports/182192 [1]
Submitted by:	Christoph Moench-Tegeder <cmt burggraben.net>
Approved by:	maintainer (timeout)

(cherry picked from commit c66307741d38eaa60380f9ba86e4f21a39cb0f12)