VS2015/2017 build fix and enable C++11 features

Patch by KindDragon from google/googletest#811

Externals/gtest/cmake/internal_utils.cmake

@@ -81,8 +81,6 @@ macro(config_compiler_and_linker)
       # Suppress "unreachable code" warning on VS 2012 and later.
       # http://stackoverflow.com/questions/3232669 explains the issue.
       set(cxx_base_flags "${cxx_base_flags} -wd4702")
-    endif()
-    if (NOT (MSVC_VERSION GREATER 1900))  # 1900 is Visual Studio 2015
       # BigObj required for tests.
       set(cxx_base_flags "${cxx_base_flags} -bigobj")
     endif()