Don't compare connections from different IP protocol versions

This provoked "Conditional jump or move depends on uninitialised value(s)"
when an IPv4 connection and an IPv6 connection generated the same hash.
Fix memory leak on TCP signature freeing
Fix memory leak when adding a service with more than one protocol
Fix memory leak when printing TCP signatures
Fix IPv6 netmask debug trace
Merge pull request #39 from madmac2501/master

Multiple bugfixes from madmac2501