Merge Bitcoin 0.17.1 into Unit-e, take 2

[cmihai]

Fixes #41. Blah blah blah, seeing if this fixes Mergeable.

This PR contains the changes from the latest Bitcoin 0.17.1, adapted for Unit-e. The branch is synced with master, up to revision 7e67c75. It compiles, launches, the unit and functional tests all work.

Here are some of the things that changed in Bitcoin 0.17, as compared to 0.16:

• The wallet "safe mode" was removed.
• Address "accounts" were removed from most places, and renamed to "labels" in the rest.
• Wallets can now have status flags attached to them. Right now, the only one is WALLET_FLAG_DISABLE_PRIVATE_KEYS, but 0.18 adds another one for empty wallets.
• 0.17 now supports partially-signed transactions.

[scravy]

• the travis file has a few regressions
• not sure we need these:
  • contrib/verify-commits/allow-incorrect-sha512-commits
  • contrib/verify-commits/allow-revsig-commits
  • contrib/verify-commits/allow-unclean-merge-commits
• QT was removed by us and slipped back in through this merge, the removal should be re-introduced:
  • build-aux/m4/unite_qt.m4 slipped back in
  • export QT_RCC_TEST=1and export QT_RCC_SOURCE_DATE_OVERRIDE=1 in gitian build script
  • depends/patches/qt/fix_configure_mac.patch
  • depends/patches/qt/fix_no_printer.patch
  • depends/patches/qt/fix_rcc_determinism.patch
  • depends/patches/qt/xkb-default.patch
  • depends/patches/zeromq/0002-disable-pthread_set_name_np.patch
• The link is incorrect: https://github.com/dtr-org/unit-e/pull/919/files#diff-83250cf6ca107475c7c1bb5b042c2dbdR59 - should be dtr-org/unit-e, not unit-e/unit-e. Looks like a failure by clonemachine
• Also here: https://github.com/dtr-org/unit-e/pull/919/files#diff-08364022658e8ca66d36bb37458857a1R57 https://github.com/unite/bips/blob/master/bip-0064.mediawiki

I just stumbled across the build instructions for OpenBSD, NetBSD, FreeBSD. I wonder if we have the capability to build on these systems? Virtual VM maybe?

[scravy]

Did we, as a safety measure, run the 0.16 tests which we have still on some branch against this C++ again?

[cornelius]

One more thing: We need https://github.com/dtr-org/unit-e/commit/ceea2d53ff90b8fcef04a61ed5c38605015d4b08. That got lost somehow.