mathlimits: check for _WIN32 and __MINGW32__ existence
diff --git a/src/google/protobuf/stubs/mathlimits.h b/src/google/protobuf/stubs/mathlimits.h
index e603947..0e84432 100644
--- a/src/google/protobuf/stubs/mathlimits.h
+++ b/src/google/protobuf/stubs/mathlimits.h
@@ -245,7 +245,7 @@
#endif
// ========================================================================= //
-#if WIN32 && !__MINGW32__ // Lacks built-in isnan() and isinf()
+#if defined(_WIN32) && !defined(__MINGW32__) // Lacks built-in isnan() and isinf()
#define DECL_FP_LIMIT_FUNCS \
static bool IsFinite(const Type x) { return _finite(x); } \
static bool IsNaN(const Type x) { return _isnan(x); } \
