pcap: fix stats dump logic

pcap has a callback function that is called for each packet. Once a
second, it's meant to 'dump stats'. However, the timing logic was
broken, so it would actually dump stats for each packet.

By moving the stats second timer into the thread vars, next calls of
the callback will be able to use the stored time.
flowvar: initialize new memory to prevent issues on error handling
Convert Flow macros to inline functions

Convert FlowReference and FlowDeReference to inline functions for
better readability and to aid static code analyzers.
log-http: enforce hostname print limit
log-http: fix error check leading to null-deref on malloc failure during setup