QSslCipher: make QString constructor explicit

A QSslCipher is not an equivalent representation of a QString, so
the constructor that takes a QString should be explicit.

Change-Id: I4c1329d1eebf91b212616eb5200450c0861d900f
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

src/network/ssl/qsslcipher.h

@@ -57,7 +57,7 @@ class Q_NETWORK_EXPORT QSslCipher
 {
 public:
     QSslCipher();
-    QSslCipher(const QString &name);
+    explicit QSslCipher(const QString &name);
     QSslCipher(const QString &name, QSsl::SslProtocol protocol);
     QSslCipher(const QSslCipher &other);
     ~QSslCipher();