By Benjamin Horney (February 10, 2016, 6:46 PM EST) -- German engineering titan Siemens AG and Spanish wind turbine manufacturer Gamesa Corp. Tecnologica SA are in the final stages of negotiating a deal to merge their wind power businesses, Reuters reported on Wednesday. According to the report, the deal, which has been rumored since late last month, is literally on the verge of being locked in, with a source being quoted as saying the two sides are "all sitting together in Madrid at the moment." The value of the merged units could be near €10 billion ($11 billion), the report added, and would leap to the forefront of the industry, usurping Denmark's Vestas as the world's biggest wind farm maker by market share....