The Federal Home Loan Banks, which are looking for ways to boost income while serving their members, are buying up mortgages in a big way. According to new numbers released by the FHLBanks’ Office of Finance, the mortgage holdings of the Banks jumped 87.3 percent last year – from $60.55 billion to $113.44 billion. As recently as 1999, the 12 FHLBanks collectively held