[packages] fetchmail 6.3.23 update

This patch updates fetchmail to version 6.3.23

Signed-off-by: Peter Wagner <tripolar@gmx.at>

git-svn-id: svn://svn.openwrt.org/openwrt/packages@34967 3c298f89-4303-0410-b956-a3cf2f4a3e73