Refresh the extern copies of googletest and googlemock. Upstream: https://github.com/google/googletest/tree/v1.15.2 Pull Request: https://projects.blender.org/blender/blender/pulls/126895
Upgrades Glog from 0.3.5 to 0.4.0, and Gtest from 0.8.0 to 0.10.0. Hopefully this will solve compilation error on MSVC with C++17.