C++: Add support of ref-qualifier for functions.

Now the ref-qualifier (& or &&) of the function declaration
is propagated to GUI. For example,  'Refactor' -> 'Add Definition'
preserves the ref-qualifier.

Change-Id: I8ac4e1cad4e44985e94230aabbd9858a7e929fee
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

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

@@ -367,6 +367,12 @@ bool Function::isPureVirtual() const
 void Function::setPureVirtual(bool isPureVirtual)
 { f._isPureVirtual = isPureVirtual; }
 
+Function::RefQualifier Function::refQualifier() const
+{ return static_cast<RefQualifier>(f._refQualifier); }
+
+void Function::setRefQualifier(Function::RefQualifier refQualifier)
+{ f._refQualifier = refQualifier; }
+
 bool Function::isAmbiguous() const
 { return f._isAmbiguous; }