MSVC 2008 (shipped with Windows SDK 7.0.7600) is the oldest we
need to support. At least on llvmpipe, gallium/auxiliary, and util
modules. For the remaining modules (particular all OpenGL specific
code) can be built with MSVC 2013.
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>