runner test helper: added a sleep command and flush each output stream after each send
runner: added a test ensuring that no undue delay occurs when the child outputs data on stdout/err
runner test: include <memory> for unique_ptr
implemented Date::fromTimespec
runner: make use of "stdbuf" to disable output buffering for the std streams of child processes
runner_test: accept delays slightly shorter than 1 sec
runner_test: export RunnerTestHelperCommands for use by other tests
Merge branch 'master' into runner-output-no-delay