* New military base to be set up in **rthern Niger * France wants to disrupt militants regrouping in Libya * Five men linked to Islamists captured in recent weeks (Adds detail, reaction from Niger) By John Irish PARIS, Oct 2 (Reuters) - France is setting up a base in **rthern Niger as part of an operation aimed at stopping al Qaeda-linked militants from crisscrossing the Sahel-Sahara region between southern Libya and Mauritania, officials said. ...