Merge tag '0.5.3' into develop
New release cycle.
Merge tag '0.5.3.1' into develop
Minor cleanups

* Remove "exec" source code references, they are not used currently and
  won't be in the future.
Refactor target variable closure taking to be more immediate.

* Complex calls need no longer visit the closure taking helpers as
  they now do it all themselves immediately correctly.

* Class variables are created immediately with the proper provider.
Changelog updates
New pre-release.
Merge tag '0.5.3.2' into develop
Tests: Minor enhancements
Minor cleanups
Tests: Detect python debug mode from NUITKA_EXTRA_OPTIONS as well.
New pre-release.
Merge tag '0.5.3.3' into develop
Merge tag '0.5.3.4' into develop
Merge tag '0.5.3.5' into develop
Tests: Flush output of test comparisons
Minor cleanups

* Removed useless tests, adapted CPython crashing ones.

* Better to give each contraction their own parameter spec,
  otherwise variables will be shared that should not.
Windows: Added support for MinGW64 compiler

* Need to build an import library from the CPython DLL.

* Stop hard coding MinGW32 path.

* May need further work, only basic tests have been tried to far.
Windows: Disable warning of scons when providing gcc.exe or cl.exe in PATH.
Windows Standalone: Make sure the paths are unique.