C++: Ignore return type on function overrides comparison

Change-Id: I9933e1cc1fb996181e818e2ea0aff76f9255f849
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

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

@@ -347,6 +347,8 @@ public:
     bool isPureVirtual() const;
     void setPureVirtual(bool isPureVirtual);
 
+    bool isSignatureEqualTo(const Function *other) const;
+
     // Symbol's interface
     virtual FullySpecifiedType type() const;