conditionalize IPv6 support
conditionalize IPv6 support

kbandla/libdnet,jncornett/libdnet,wtfbbqhax/libdnet,kbandla/libdnet,kbandla/libdnet,wtfbbqhax/libdnet,wtfbbqhax/libdnet,jncornett/libdnet,jncornett/libdnet