MSVC and clang-cl automatically define |_WIN32| but |WIN32| is only
defined if a Windows header file has been included or if -DWIN32 was
passed on the command line. Thus, it is always better to test |_WIN32|
than |WIN32|. The convention in BoringSSL is to test |OPENSSL_WINDOWS|
instead, except for the place where |OPENSSL_WINDOWS| is defined.
Change-Id: Icf3e03958895be32efe800e689d5ed6a2fed215f
Reviewed-on: https://boringssl-review.googlesource.com/5553
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
8a36e53abb