NFD

Currently, fib::Entry::addNextHop has the following prototype

void
addNextHop(shared_ptr<Face> face, int32_t cost);

while the cost type and fib::Nexthop::setCost is uint64_t:

void
setCost(uint64_t cost);

In addition to that, test cases use uin64_t as a cost parameter and I'm not sure why compiler wasn't complaining before...