LibCpp: Support parsing function qualifiers

Author: https://github.com/itamar8910
Commit: 1f9f6ea9d6
Pull-request: https://github.com/SerenityOS/serenity/pull/6009

Userland/Libraries/LibCpp/AST.h

@@ -171,6 +171,7 @@ public:
 
     virtual NonnullRefPtrVector<Declaration> declarations() const override;
 
+    Vector<StringView> m_qualifiers;
     RefPtr<Type> m_return_type;
     NonnullRefPtrVector<Parameter> m_parameters;
     RefPtr<FunctionDefinition> m_definition;