Request Softwire46 (S46) [RFC 7598] options when the map and/or ds-lite
packages are installed. This is required as the behaviour of odhcp6c has
changed to not include these OROs by default.
See openwrt/odhcp6c#89
Signed-off-by: Richard Patterson <richard@helix.net.nz>
Signed-off-by: Shengyu Qu <wiagn233@outlook.com>