GitLab

Reduces the flakiness of gtest-port_test on Mac; improves the Python tests; hides methods that we don't want to publish; makes win-dbg8 the default scons configuration (all by Vlad Losev).

Adds sample4_unittest to scons (by Vlad Losev); adds logic for getting the thread count on Mac (by Vlad Losev); adds HasFailure() and HasNonfatalFailure() (by Zhanyong Wan).

Implements death tests on Windows (by Vlad Losev); enables POSIX regex on Mac and Cygwin; fixes build issue on some Linux versions due to PATH_MAX.