CVS: Modernize

* Use pragma once
* Use some more overrides
* Tiny clean-ups here and there

Change-Id: I951afa8ed31c5f414d4ae872c79f80db19909ee0
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/cvs/cvscontrol.h

@@ -23,8 +23,7 @@
 **
 ****************************************************************************/
 
-#ifndef CVSCONTROL_H
-#define CVSCONTROL_H
+#pragma once
 
 #include <coreplugin/iversioncontrol.h>
 
@@ -67,10 +66,8 @@ public:
     void emitFilesChanged(const QStringList &l);
 
 private:
-    CvsPlugin *m_plugin;
+    CvsPlugin *const m_plugin;
 };
 
 } // namespace Internal
 } // namespace Cvs
-
-#endif // CVSCONTROL_H