a191e23b8e doc: Add release notes (Hennadii Stepanov)
ae749d12dd doc: Add libnatpmp stuff (Hennadii Stepanov)
e28f9be87a ci: Add libnatpmp-dev package to some builds (Hennadii Stepanov)
5a0185b6c9 gui: Add NAT-PMP network option (Hennadii Stepanov)
a39f7336a3 net: Add -natpmp command line option (Hennadii Stepanov)
28acffd9d5 net: Add NAT-PMP to port mapping loop (Hennadii Stepanov)
a8d9f275d0 net: Add libnatpmp support (Hennadii Stepanov)
58e8364dcd gui: Apply port mapping changes on dialog exit (Hennadii Stepanov)
cf151cc68c scripted-diff: Rename UPnP stuff (Hennadii Stepanov)
4e91b1e24d net: Add flags for port mapping protocols (Hennadii Stepanov)
8b50d1b5bb net: Keep trying to use UPnP when -upnp=1 (Hennadii Stepanov)
28e2961fd6 refactor: Replace magic number with named constant (Hennadii Stepanov)
02ccf69dd6 refactor: Move port mapping code to its own module (Hennadii Stepanov)
Pull request description:
Close#11902
This PR is an alternative to:
- #12288
- #15717
To compile with NAT-PMP support on Ubuntu [`libnatpmp-dev`](https://packages.ubuntu.com/source/bionic/libnatpmp) should be available.
Log excerpt:
```
2020-02-05T20:12:28Z [mapport] NAT-PMP: public address = 95.164.65.194
2020-02-05T20:12:28Z [mapport] AddLocal(95.164.65.194:18333,3)
2020-02-05T20:12:28Z [mapport] NAT-PMP: port mapping successful.
```
See: [`libnatpmp`](https://miniupnp.tuxfamily.org/libnatpmp.html)
---
Some follow-ups are out of this PR's scope:
- mention NAT-PMP library in the version message
- ~integrate NAT-PMP into the GUI~ (already [added](https://github.com/bitcoin/bitcoin/pull/18077#issuecomment-589405068))
ACKs for top commit:
laanwj:
Tested and code review ACK a191e23b8e
Tree-SHA512: 10e19267c21bf30f20ff1abfc882d526049f0e790b95e12f109dc2bed7c0aef45de03eaf967f4e667e7509be04f1873a5c508087393d947205f3aab2ad6d7cf1