Refactored CPU mipmap generation and added 3D texture mipmap generation functions. TRAC #22926 Signed-off-by: Jamie Madill Signed-off-by: Nicolas Capens Author: Geoff Lang git-svn-id: https://angleproject.googlecode.com/svn/branches/es3proto@2277 736b8ea6-26fd-11df-bfd4-992fa37f6226