Fix the check conditions in config-msvc.mak and info-msvc.mak so that
the ICU items does indeed get built into the HarfBuzz main DLL, and that
the correct configuration info is displayed.

Also update the checks in detectenv-msvc.mak so that we can detect that
we are using Visual Studio 2017 (although the 2015-built binaries use
the same CRT DLL as the 2017 ones).