64fb0ac Declare single-argument (non-converting) constructors "explicit" (practicalswift)
Pull request description:
Declare single-argument (non-converting) constructors `explicit`.
In order to avoid unintended implicit conversions.
For a more thorough discussion, see ["C.46: By default, declare single-argument constructors explicit"](http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c46-by-default-declare-single-argument-constructors-explicit) in the C++ Core Guidelines (Stroustrup & Sutter).
Tree-SHA512: e0c6922e56b11fa402621a38656d8b1122d16dd8f160e78626385373cf184ac7f26cb4c1851eca47e9b0dbd5e924e39a85c3cbdcb627a05ee3a655ecf5f7a0f1
6e8c48dc5 Add const to methods that do not modify the object for which it is called (practicalswift)
Pull request description:
Tree-SHA512: a6888111ba16fb796e320e60806e1a77d36f545989b5405dc7319992291800109eab0b8e8c286b784778f41f1ff5289e7cb6b4afd7aec77f385fbcafc02cffc1
1f668b6 Expose if CScheduler is being serviced, assert its not in EmptyQueue (Matt Corallo)
3192975 Flush CValidationInterface callbacks prior to destruction (Matt Corallo)
08096bb Support more than one CScheduler thread for serial clients (Matt Corallo)
2fbf2db Add default arg to CScheduler to schedule() a callback now (Matt Corallo)
cda1429 Give CMainSignals a reference to the global scheduler (Matt Corallo)
3a19fed Make ValidationInterface signals-type-agnostic (Matt Corallo)
ff6a834 Use TestingSetup to DRY qt rpcnestedtests (Matt Corallo)
Tree-SHA512: fab91e34e30b080ed4d0a6d8c1214910e383c45440676e37be61d0bde6ae98d61e8903d22b846e95ba4e73a6ce788798350266feba246d8a2ab357e8523e4ac5
On a busy or slow system, the CScheduler unit test could fail because it
assumed all threads would be done after a couple of milliseconds.
Replace the hard-coded sleep with CScheduler stop() method that
will cleanly exit the servicing threads when all tasks are completely
finished.
