fix off-by-one in interface alias handling. reported by Jose Nazario and Scott Dawson <{jose,sdawson}@arbor.net>
fix off-by-one in interface alias handling. reported by Jose Nazario and Scott Dawson <{jose,sdawson}@arbor.net>

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