ROTTERDAM (Reuters) - Royal KPN NV, the largest Dutch telecommunications company, on Wednesday reported better than expected fourth quarter earnings despite weak mobile services revenue and said it expects "stable to slightly growing" core earnings in 2020.CEO Joost Farwerck, who took the top job in October amid a wider overhaul, said he will continue with plans to cut costs while investing in fibre optic and 5G networks.Competition from the likes of T-Mobile and Vodafone-Ziggo were "reflected..