Fixes for gcc 7
This fixes a few issues when using a newer compiler (in my case gcc 7.1.1) available in for example Arch Linux.
Solves for example this issue: https://github.com/zcash/zcash/issues/2304
The first thing is an error when checking for boost_system and is solved by disabling that warning (wich is treated as an error and, hence, stops the build):
```
configure:22242: checking for exit in -lboost_system-mt
configure:22267: g++ -m64 -o conftest -std=c++11 -pipe -fPIC -O1 -fwrapv -fno-strict-aliasing -Werror -g -Wformat -Wformat-security -Wstack-protector -fstack-protector-all -fPIE ..<snip>... /x86_64-unknown-linux-gnu/share/../lib conftest.cpp -lboost_system-mt -lanl >&5
conftest.cpp:70:6: error: declaration of 'char exit()' conflicts with built-in declaration 'void exit(int)' [-Werror=builtin-declaration-mismatch]
char exit ();
^~~~
cc1plus: all warnings being treated as errors
```
The second thing was to clean some code that is deprecated in C++11 which also lead to a warning treated as error. It could also be fixed with `-Wno-deprecated` but better to fix the issue in my opinion.
--nocleanup is sufficient to leave the data directories behind. --noshutdown is
only useful if you want to inspect the nodes afterwards, and you'd need to
manually shut down both nodes before copying the data directories.
Fix deprecation policy comment.
Thanks to @daira for spotting this and suggesting the correct policy.
Feel free to adjust wording, this is primarily to track the issue and suggest a potential fix.
Ansible works with Python 2.6 and 2.7, but Buildbot requires 2.7. Both have
at least preliminary Python 3 support, but until our RPC tests are migrated to
Python 3, we need to use Python 2 for testing, and so this requirement stands.
Previously various user-facing strings have used inconsistent currency units "BTC",
"btc" and "bitcoins". This adds a single constant and uses it for each reference to
the currency unit.
Also adds a description of the unit for --maxtxfee, and adds the missing "amount"
field description to the (deprecated) move RPC command.
Corrections are to the median block times, which were generated by subtracting
CBlockIndex::nMedianTimeSpan / 2 from the block height and then multiplying by
the target spacing. GetMedianTimePast() takes an array sorted by std::sort() and
returns element CBlockIndex::nMedianTimeSpan / 2, meaning that if
CBlockIndex::nMedianTimeSpan is odd (which it is), there is an out-by-one error
in the subtraction.
Fixes#2480 where missing map entry would cause a segfault.
`wtxHeight = mapBlockIndex[wtx.hashBlock]->nHeight;` results in undefined behaviour when the block hash is not present in the map, returning a null value which is dereferenced via `->nHeight`. This error is triggered by a zero-conf wallet transaction which has not been mined yet. As discussed in #2480, on some systems there is a segfault whilst on others there is a silent exit. This makes it difficult to write a test, but the fix has been tested empirically to confirm an exception is thrown. This PR fixes the segfault and complements #2525 which prevents a user from sending from a zaddr with minconf 0.
Ansible playbook for configuring CI workers
The playbook in this PR can be used for configuring common Unix variants to run a Buildbot worker for the Zcash CI, starting from a fresh install (or a VM template provided by a hosting service).
