SVN: Escape files containing '@' characters

Append a '@' to files with a '@' in their name. The last '@' (and
everything following it) is cut off by SVN and treated as a revision.

Task-number: QTCREATORBUG-17229
Change-Id: Icab62345c18277c0327b1e548a45feda0906b3c3
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/subversion/subversionclient.h

@@ -71,6 +71,9 @@ public:
 
     QString synchronousTopic(const QString &repository);
 
+    static QString escapeFile(const QString &file);
+    static QStringList escapeFiles(const QStringList &files);
+
 protected:
     Core::Id vcsEditorKind(VcsCommandTag cmd) const override;