After a slow 2012, mergers and acquisitions involving the state’s banks have heated up, according to SNL Financial LC of Charlottesville, Va. Banks mostly fed on in-state deals in 2013 but have focused more this year on buying peers in nearby states. Nationally there were 5,876 commercial banks at the end of last year, about half as many as 20 years ago. Increased regulatory costs and slim interest margins are squeezing profits and spurring sales.