Deprecate enumerators fro SSL v.2 and v.3 protocols

And we'll get rid of them in Qt 6.

Task-number: QTBUG-75638
Change-Id: I34764f93bf579da0640a930d9160783ea9c8317d
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/network/ssl/qssl.h

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtNetwork module of the Qt Toolkit.
@@ -77,9 +77,11 @@ namespace QSsl {
 #endif
 
     enum SslProtocol {
+#if QT_DEPRECATED_SINCE(5, 15)
         SslV3,
         SslV2,
-        TlsV1_0,
+#endif
+        TlsV1_0 = 2,
 #if QT_DEPRECATED_SINCE(5,0)
         TlsV1 = TlsV1_0,
 #endif