* Suppressions: merged `isSuppressedLocal()` into `isSuppressed()`
* avoid some unnecessary copies when adding suppressions
* TestSuppressions: improved readability of multiple line string literals
* supressions.h: got rid of unnecessary copy and assignment operators for `Suppressions::Suppression` - fixes `performance-move-const-arg` clang-tidy warning
* TestSuppressions: cleaned up a variable construction
* added asserts to make sure executors are only used in the intended context
* TestSuppressions: specify proper job counts in `checkSuppression*()`
* TestSuppressions: enabled all asserts in `runChecks()`
* TestSuppressions: removed unnecessary setting from `checkSuppression()`
* TestSuppressions: small cleanup in the way tests are called
* TestSuppressions: use `SingleExecutor`
* added `Settings::useSingleJob()` and use it instead of checking `jobs` or `jointSuppressionReport`
* extracted single job execution into `SingleExecutor`
* moved `reportStatus()` from `CppCheckExecutor` to Èxecutor
* TestSingleExecutor: improved tests
* added testing of markup extension handling in executors
* cleaned up includes based on `include-what-you-use`
* testsingleexecutor.cpp: suppress `performance-unnecessary-value-param` clang-tidy warnings
* ProcessExecutor: send color via pipe instead of applying it beforehand
* do not unconditionally apply colors to output / disable all colors in tests / adjusted tests for changed output behavior
* fixed precision loss in `Executor::reportStatus()`
* fixed `naming-varname` selfcheck warnings
* iwyu.yml: use debian:unstable to always get latest include-what-you-use
* cleaned up includes based on include-what-you-use
* mitigated include-what-you-use false positives
* fixed functionConst findings and enabled it in selfcheck
* fixed functionStatic findings and enabled it in selfcheck
* .travis_suppressions: adjusted comment
* testimportproject.cpp: added missing asserts
* use range loops
* removed redundant string initializations
* use nullptr
* use proper boolean false
* removed unnecessary continue from end of loop
* removed unnecessary c_str() usage
* use emplace_back()
* removed redundant void arguments