C++: Automatic Doxygen comment blocks generation

This improves our completion support for documentation
comments. It's now possible to have a Doxygen block
generated when hitting enter after a /** or /*! comment
start. A couple other related options are also available.

Task-number: QTCREATORBUG-2752
Task-number: QTCREATORBUG-3165

Change-Id: I1c81c0b4b370eb1d409ef72a9c7f22c357f202f4
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@nokia.com>
Reviewed-by: Christian Kamm <christian.d.kamm@nokia.com>

src/plugins/cpptools/cpptoolssettings.h

@@ -40,7 +40,7 @@
 namespace CppTools
 {
 class CppCodeStylePreferences;
-
+class CommentsSettings;
 
 namespace Internal
 {
@@ -61,6 +61,10 @@ public:
     static CppToolsSettings *instance();
 
     CppCodeStylePreferences *cppCodeStyle() const;
+    const CommentsSettings &commentsSettings() const;
+
+signals:
+    void commentsSettingsChanged(const CppTools::CommentsSettings &settings);
 
 private:
     Internal::CppToolsSettingsPrivate *d;