Libpcap

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- Add support for Python 3.8.
- Drop support for Python 3.4.
- Drop support for Python 2.
- Upgrade to the latest libpcap API 1.10.0-PRE
- Establishing npcap as default backend.
- Internal npcap's dll-s have been removed due to ev. license problems.
- | Add support for Linux x64:
| add internal tcpdump's libpcap.so v.1.9.1 with remote capture support.
| system's tcpdump's libpcap.so can also be used (via libpcap.libpcap.cfg).
- Added ReadTheDocs config file.
- Setup update and cleanup.

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- Upgrade to the latest libpcap API 1.10.0-PRE
- Upgrade npcap's libpcap dll-s to the 0.996
- Minor setup fixes and improvements.

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- Upgrade to the latest libpcap API 1.10.0-PRE
- Upgrade npcap's libpcap dll-s to the 0.99rc9
- Update required setuptools version.
- Minor setup improvements.
- Updates of tests.

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- Upgrade to the latest libpcap API 1.10.0-PRE
- Upgrade npcap's libpcap dll-s to the 0.99rc7
- Update required setuptools version.

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- Update required setuptools version.

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- Upgrade npcap's libpcap dll-s to the 0.99rc5