Import the busybox-1.23.1 uuencode/base64 helper functions.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Steffen Trumtrar authored on 2 Sep 2015 Sascha Hauer committed on 12 Apr 2019