Nethuns v3.1.0

Fix for C++20 shared_ptr

File Pcap does not support capture direction. Ignoring it...

CMakeFiles: building nethuns as sub git project enabled.

Warning fixed.

Merge branch 'dev'

Merge pull request #4 from larthia/nmreplay

port of nmreplay from netmap

License headers added.

Merge pull request #3 from larthia/fix-tests2

Implement nethuns_send and fix nethuns_bind for netmap

Merge branch 'dev'