Throw is serial won't fit into uint32_t, fixes #1009
Renamed strtoui to pdns_strtoui, requested by @ahu
Merge pull request #1864 from cmouse/check-serial-overflow

Check serial overflow
prevent warnings on 32 bit
Allow changing the Sockaddr in ComboAddress
Reuse existing connection when possible
Merge pull request #1868 from cmouse/remotebackend-keepalive

Remotebackend keepalive support