Rename the Visual Studio >= 10 generators to indicate the version year:
Visual Studio 10 => Visual Studio 10 2010
Visual Studio 11 => Visual Studio 11 2012
Visual Studio 12 => Visual Stduio 12 2013
Report the names with the year to the list of available generators so
that the cmake-gui drop-down shows the years. When selecting a
generator from the "-G" option or from an existing CMAKE_GENERATOR cache
entry, recognize names without the years for compatibility and map them
to the names with years.
Update the generator names in the cmake-generators.7 manual.
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