Fill readme file for Win32 platform

[JeromeMigne]

Provide details about rpcapd compilation inside Visual Studio IDE.

These details were missing to compile rpcapd over Npcap for Windows platform.

[guyharris]

By this are you referring to the built-in CMake support introduced in Visual Studio 2017?

If so, please note that:

• you should say "Visual Studio 2017 or later", not just "a recent version";
• you don't necessarily need VS 2017 or later to build, but if you have an earlier version, you'll have to run CMake yourself to generate the .prj and .sln files for VS.

Note also that there is no need to run the Visual Studio IDE to build libpcap (or tcpdump or Wireshark or...) - you can just use msbuild.

[JeromeMigne]

Updated.

[JeromeMigne]

When opening the folder with Visual Studio 2019, without any modification:

• the following CMake error occurs: Neither flex nor win_flex nor lex was found,
• ENABLE_REMOTE is set by default to YES,
• PACKET_TYPE is not set and after having resolved all other settings, it compiles with pcap-null.

And -DCMAKE_PREFIX_PATH=\"C:\\path\\to\\npcap-sdk-1.03\" -DENABLE_REMOTE=YES does not resolve this.

[guyharris]

I've updated the document to give details about downloading and installing required components and about configuring and building with the VS 2017 GUI, the VS 2019 GUI, and the command line. I tested the instructions with VS 2017 on Windows 7 and VS 2019 on Windows 10.

[daluu]

Thanks for the README update. I would say however, that some changes in this PR that did not make it to the actual README, are more helpful to a newbie to cmake + Visual Studio config, like the cmake variables that point to lex & yacc. It's more clear from this PR about it. And from comparing the two, I guess setting PCAP_TYPE to npf is unnecessary?