Assume that MSVC supports C++11.

MSVC doesn't define __cplusplus as 201103 to indicate C++11 support, so
just assume that the compiler supports C++11 if _MSC_VER is defined.

Change-Id: I27f6eeefe6e8dc522470f36fab76ab36d85eebac
Reviewed-on: https://boringssl-review.googlesource.com/8734
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/include/openssl/ec_key.h b/include/openssl/ec_key.h
index 78b2f25..5b0f516 100644
--- a/include/openssl/ec_key.h
+++ b/include/openssl/ec_key.h
@@ -323,7 +323,7 @@
 #if defined(__cplusplus)
 }  /* extern C */
 
-#if __cplusplus >= 201103
+#if defined(BORINGSSL_HAVE_CXX11)
 
 namespace bssl {