CPlusPlus: Add toLink method to the Symbol

Basically move it from CppTools to CPlusPlus
to be able to use it there.

Change-Id: I0af80f93bdc029824397ceafdf940cb86c4382b0
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/libs/3rdparty/cplusplus/Symbol.h

@@ -22,6 +22,7 @@
 
 #include "CPlusPlusForwardDeclarations.h"
 
+namespace Utils { struct Link; }
 
 namespace CPlusPlus {
 
@@ -197,6 +198,8 @@ public:
     /// Returns true if this Symbol is an Objective-C @property declaration.
     bool isObjCPropertyDeclaration() const;
 
+    Utils::Link toLink() const;
+
     virtual const Scope *asScope() const { return 0; }
     virtual const Enum *asEnum() const { return 0; }
     virtual const Function *asFunction() const { return 0; }