Added sse2 acceleration for highbitdepth variance

Change-Id: I446bdf3a405e4e9d2aa633d6281d66ea0cdfd79f
(cherry picked from commit d7422b2b1eb9f0011a8c379c2be680d6892b16bc)
(cherry picked from commit 6d741e4d76a7d9ece69ca117d1d9e2f9ee48ef8c)
Merge "Added sse2 acceleration for highbitdepth variance"