Google Test 1.7.0 is severely outdated and should be upgraded

[StephanTLavavej]

I'm the primary maintainer of Microsoft's C++ Standard Library. The MSVC team regularly builds popular open-source projects, including yours, with development versions of the build tools in order to find and fix regressions in the compiler and libraries before they can ship and cause trouble for the world. This also allows us to provide advance notice of breaking changes, which is the case here.

I'm working on completely removing MSVC's legacy implementation of TR1, which was superseded by C++11, in microsoft/STL#5763. We've already removed it by default in C++17 mode and later (with an escape hatch) and have emitted deprecation warnings since VS 2017 15.5 in Dec 2017, warning that "The non-Standard std::tr1 namespace and TR1-only machinery are deprecated and will be REMOVED."

This affects bullet3 because it uses an ancient checked-in copy of Google Test, which was using TR1. After removing TR1, this emits a compiler error:

C:\gitP\bulletphysics\bullet3\test\gtest-1.7.0\include\gtest\gtest-printers.h(532,34): error C2039: 'tr1': is not a member of 'std' [C:\gitP\bulletphysics\bullet3\build_amd64\test\gtest-1.7.0\gtest.vcxproj]

Google Test's usage of TR1 was fixed many years ago, I believe by google/googletest@7d3b73c in Oct 2018. (I'm not sure how old Google Test 1.7.0 is, but it's older than 1.8.1 released in Aug 2018.)

bullet3 should upgrade its checked-in copy of Google Test, ideally to the latest released version, but at least to a more recent version containing its removal of TR1 usage.