npcap to work with similar behavior as WinPcap

[trivalik]

I fixed the outstanding to able to work with this library:

• npcap to work with similar behavior as WinPcap
• run unit tests without physical adapter is default, in case real adapter verification is necessary, declare REAL define
• .NET Framework 4 capable, since I needed it
• take over solution Fix marshalling of StringBuilder errors dotpcap/sharppcap#533 to receive errors from pinvoke, before was broken

Feedback is welcome.

[klaus0x7c4]

Thanks for the PR! Sry for late response. I will have a lool :-)

[trivalik]

• pcap_open_live is required for linux/unix, there is no pcap_open
• using pcap_hopen_offline is necessary for WinPcap

[trivalik]

Since there is no issue section:
NotEqual fails randomly with symmetrical IP addresses

Pcap.Net/PcapDotNet/src/PcapDotNet.Packets.Test/IpV4AddressTests.cs

Line 70 in 64a07d6

Assert.NotEqual(address, buffer.ReadIpV4Address(0, Endianity.Small));