Vcs: in VcsBaseClient use functors to create log/diff parameter widgets

Also API of VcsBaseEditorParameterWidget was changed to take benefit of C++11 lambdas.
Slot executeCommand() is no longer virtual and only fires signal commandExecutionRequested().
The Vcs client just has to bind a lambda to this signal instead of some boiler-plate code
like keeping track of the arguments of diff/log with "struct XxxDiffParameters", etc.

Change-Id: I347c97d84a8324e9c661df4e6d9a6075980b020f
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>

src/plugins/cvs/cvsclient.h

@@ -53,14 +53,9 @@ public:
     QStringList revisionSpec(const QString &revision) const;
     StatusItem parseStatusLine(const QString &line) const;
 
-
 protected:
     Utils::ExitCodeInterpreter *exitCodeInterpreter(VcsCommandTag cmd, QObject *parent) const;
     Core::Id vcsEditorKind(VcsCommandTag cmd) const;
-    VcsBase::VcsBaseEditorParameterWidget *createDiffEditor(const QString &workingDir,
-                                                            const QStringList &files,
-                                                            const QStringList &extraOptions);
-private:
 };
 
 } // namespace Internal