Filter compiler: exclude NULL character from STRING definition.
Stop parsing if unknown data offset is used.
Filter compiler: more fixes against null pointer dereference
Filter compiler: fix null dereference in a specific case
Merge pull request #561 from tomaszn/master

Filter compiler: fix some null pointer dereferences
replace obsolete gethostbyaddr() with getnameinfo()
threadize host resolution process
start host resolution when option is acitivated (GTK and Curses)
add IPv6 for passive name resolution
update TODO
Merge pull request #568 from koeppea/rework-dns-resolution

Rework DNS resolution