CPlusPlus: Support structured bindings

While we do recommend clangd for modern code bases, we should still be
able to parse basic language constructs.

Fixes: QTCREATORBUG-27975
Change-Id: I189b991685a5cd5f62f2afce77878b60c895e8f9
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: hjk <hjk@qt.io>

src/libs/cplusplus/FindUsages.cpp

@@ -2494,6 +2494,13 @@ bool FindUsages::visit(DeclaratorIdAST *ast)
     return false;
 }
 
+bool FindUsages::visit(DecompositionDeclaratorAST *ast)
+{
+    for (auto it = ast->identifiers->begin(); it != ast->identifiers->end(); ++it)
+        name(*it);
+    return false;
+}
+
 bool FindUsages::visit(NestedDeclaratorAST *ast)
 {
     // unsigned lparen_token = ast->lparen_token;