CPlusPlus: Support C++11 attributes also for function parameters

Fixes: QTCREATORBUG-24636
Change-Id: I9dc3d2cc6ca102b09f6b040455fa901c362dae7d
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

tests/auto/cplusplus/ast/tst_ast.cpp

@@ -1338,7 +1338,7 @@ void tst_AST::cpp11_variadic_inheritance()
 void tst_AST::cpp11_attributes()
 {
     QSharedPointer<TranslationUnit> unit(parseDeclaration(
-        "[[noreturn]] void f() {throw \"error\";}",
+        "[[noreturn]] void f([[maybe_unused]] int v) {throw \"error\";}",
         false, false, true));
     AST *ast = unit->ast();
     QVERIFY(ast != nullptr);