LONDON (Reuters) - British listed private equity company 3i posted a half-year return of 10%, helped by good trading performance across its portfolio including infrastructure, it said on Thursday.3i completed new investments in Magnitude Software and Evernex and made seven bolt-on acquisitions for its portfolio companies in the first half."Despite the uncertain macroeconomic environment, the majority of our investments have moved into the second half of the year with decent momentum," Chief..