European shares close slightly higher ahead of Christmas shutdown; Aviva to buy Direct Line in $4.6 billion deal / Direct Line Shares Rise on Revised Aviva Bid / Direct Line set to accept sweetened Aviva takeover bid / Aviva Reaches Preliminary Deal With Direct Line on Takeover / Aviva raises offer to buy Direct Line / Why Direct Line Should Accept Aviva's Offer / Direct Line Shares Surge 40% as it Rejects Aviva Offer / Direct Line shares soar as it rejects UK rival's £3.3bn takeover offer / Europe stocks close higher; Direct Line soars 41% after rejecting Aviva bid / Direct Line shares surge 37% after insurer rejects Aviva bid