libvpx

Enable SSSE3 inverse 2D-DCT with 10 non-zero coeffs

This commit enables SSSE3 implementation of the inverse 2D-DCT
with only first 10 coefficients non-zero. It reduces the runtime
of SSE2 version from 745 cycles to 538 cycles, i.e., 27% speed-up.

Change-Id: I18ba4128859b09c704a6ee361d69a86c09fe8dfe