Use internal namespace in VCSBase more consistently

Change-Id: I61de9796aaeb9484b44029c5f1d46e69834a04c3
Reviewed-by: Hugues Delorme <delorme.hugues@fougsys.fr>

src/plugins/vcsbase/nicknamedialog.cpp

@@ -61,7 +61,8 @@ namespace Internal {
 
 // For code clarity, a struct representing the entries of a mail map file
 // with parse and model functions.
-struct NickNameEntry {
+class NickNameEntry {
+public:
     void clear();
     bool parse(const QString &);
     QString nickName() const;