openvpn: fix compile error with musl

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@41425 3c298f89-4303-0410-b956-a3cf2f4a3e73
odhcpd: some minor DHCP/DHCPv6 fixes

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@41432 3c298f89-4303-0410-b956-a3cf2f4a3e73