Revert "Drop VS 2010 support."
Revert "Drop VS 2010 support."

This reverts commit 5105f3f265c60a25babb76096d962de3c9838f77.

This commit should be groonga repo.

yoku0825/mroonga,naoa/mroonga,naoa/mroonga,mroonga/mroonga,yoku0825/mroonga,yoku0825/mroonga,mroonga/mroonga,mroonga/mroonga,naoa/mroonga,naoa/mroonga,mroonga/mroonga,yoku0825/mroonga,yoku0825/mroonga,yoku0825/mroonga,naoa/mroonga,naoa/mroonga